Millionaire’s shortbread is a rich and decadent cookie bar with layers of shortbread, buttery salted caramel, and silky dark chocolate ganache. If you love Twix bars, then you’ll love this gourmet, homemade version. Sprinkle the bars with flaky salt for a totally indulgent sweet and salty treat!
And even though there are three separate layers to prepare, these millionaire’s shortbread bars are actually very easy to make, using my favorite, foolproof method for cooking caramel. It takes no time at all to prepare these bars. The hardest part is waiting for them to cool so you can cut them into those gorgeous, tempting squares.
Looking for more recipes like this? You’ll love these fudge brownie shortbread bars, chocolate chip oatmeal cookie bars, and gooey pecan pie bars.
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Why is it Called Millionaire’s Shortbread?
These incredibly decadent caramel shortbread bars are called Millionaire’s Shortbread because they’re so rich and indulgent. Also known as caramel slice, caramel squares, caramel shortcake and millionaire’s slice, these cookie bars feature three layers that look just stunning when cut into squares.
The Shortbread
The cookie base is a simple shortbread made of flour, sugar and butter, with a little salt and vanilla to enhance the flavors. It’s easy to make by just pressing the crumbs into a pan and baking it briefly.
The Caramel
The next layer is salted caramel that’s so soft, chewy and buttery. Most popular recipes call for cooking the caramel on the stove, which can be a tedious, lengthy and finicky process. But I use my foolproof method for cooking the caramel quickly and effortlessly in the microwave, which makes this the easiest and best millionaire’s shortbread recipe you’ll find.
The Chocolate
The final layer is the chocolate. Some recipes call for nothing more than melted chocolate spread over the caramel, and others a chocolate ganache made of chocolate and butter. But both of those can crack and lose their glossy shine, so I’ve made a classic chocolate ganache of dark chocolate and heavy whipping cream. It stays soft, silky and shiny, and the bittersweet chocolate is the perfect foil to the sweet caramel. A sprinkling of flaky Maldon sea salt adds sparkle and a lovely salty-sweet balance to these rich shortbread bars.
Ingredients
Crust.
A classic shortbread cookie or crust is usually composed of just flour, sugar and butter. I’ve also added a pinch of salt, and vanilla extract, for more flavor.
Caramel.
For the caramel, you’ll need light corn syrup, sweetened condensed milk, granulated sugar, dark brown sugar, unsalted butter, salt and vanilla extract.
Chocolate.
Classic chocolate ganache is made with equal parts heavy whipping cream and chocolate. I prefer dark chocolate, around 55-65% cacao, to balance the sweetness of the caramel, but you can use a sweeter chocolate if you prefer. One of my favorite brands of chocolate for baking is Chocolove. I wouldn’t recommend using chocolate chips for ganache, since they don’t melt as smoothly. A sprinkling of flaky Maldon sea salt is the perfect finish.
Tools and Equipment
8-Inch Baking Pan + Parchment Paper.
You’ll need to line your baking pan with two sheets of parchment paper, so that the paper comes all the way up the sides of the pan. This makes it easy to lift the bars out of the pan to cut them, and ensures the chewy caramel won’t stick to the pan.
Microwaveable Bowl.
I recommend a glass Pyrex bowl with a 2.5 quart capacity for cooking the caramel in the microwave.
Digital Instant Read Thermometer.
A thermometer is necessary to check the temperature of the caramel. For caramel and candy cooked on the stove, you’d typically use a candy thermometer. But since we’re cooking the caramel in the microwave, a standard probe thermometer (like one to check the internal temperature of meat) works well.
Saucepan + Metal Bowl (Double Boiler).
Double boilers are great for gently cooking or warming ingredients that shouldn’t be cooked over direct heat, like custards and lemon curd. No one really needs a special double boiler, because if you have saucepans and metal mixing bowls, then all you need to do is fill the pan with a few inches of water and set the bowl on top of the pan to make a double boiler. We’ll be using this method to gently warm the chocolate and cream for the ganache.
Instructions
Bake the Shortbread.
- The shortbread crust is quick and easy to make. Simply combine all the ingredients in a bowl, and cut the butter into the dry ingredients with a pastry cutter, until moist and crumbly. Then press the crumbs evenly into the bottom of the prepared pan.
- Bake at 350 F for 20 minutes, until pale golden brown. Then set aside to cool briefly before making the caramel.
Cook the Caramel.
Once you’ve cooked caramel in the microwave, you’ll never go back to cooking it on the stove again! I discuss this process in length in my salted caramels recipe, so be sure to give that a read.
- In a large microwave-safe bowl (I recommend a glass Pyrex bowl with a 2.5 quart capacity), whisk together the melted butter, corn syrup, granulated sugar, brown sugar, sweetened condensed milk and salt until smooth.
- Place the bowl in your microwave, uncovered. Microwave on high for 6 minutes, then stir and check the temperature with a digital instant read thermometer. The temperature of the caramel needs to reach between 238-242 degrees F. If the caramel isn’t hot enough, continue to microwave on high in 15-second increments, checking the temperature each time until it reaches the correct temperature.My microwave is 1,000 watts, and it usually takes around 6 1/2 minutes.
- Remove the caramel from the microwave, and immediately stir in the vanilla until smooth. The caramel will bubble and hiss a little.
- Pour the hot caramel over the cooled crust. Let the bars sit at room temperature to cool for 1 hour, then refrigerate until both the crust and the caramel are completely cooled and firm, about 1 – 1 1/2 hours.
Finish with Ganache.
- Set up a double boiler (a pan of simmering water with a heatproof bowl sitting on top of the pan – the bottom of the bowl should not touch the water).
- Measure the chocolate and cream into the bowl. Let the mixture warm until the chocolate melts, then stir the ganache with a spatula until smooth and shiny.
- Immediately pour the ganache over the cooled caramel, and smooth out the ganache. Let the bars sit at room temperature to let the ganache set for about 30 minutes, then refrigerate until the ganache is firm.
How to Cut Millionaire’s Shortbread
These bars are best eaten at room temperature when the caramel is soft and luscious. But when you cut the bars, you want them to be chilled and firm enough to cut cleanly, although not rock hard from the fridge.
- Once the ganache has set, take the bars out of the fridge. Lift the bars out of the pan by grabbing onto the parchment paper. Pull the paper away from the sides of the bars, and then slide the whole slab of bars off the paper and onto a cutting board.
- Press against the caramel around the edges. If it’s soft enough that you can make an impression, then they’re ready to be cut. You don’t want to let them warm up enough that the caramel gets soft and gooey, or they will be hard to cut cleanly, and you’ll need to chill them again before cutting.
- Use a large, sharp chef’s knife to cut straight down, cutting the whole slab in half. Slide the knife out sideways, not back up through the bars. Then cut each half into 8 squares, for a total of 16 squares. To keep the bars looking neat, wipe the knife clean in between cuts.
- Before serving, sprinkle the bars with the flaky salt.
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Millionaire’s Shortbread
All recipes on Curly Girl Kitchen are developed for high altitude at 5,280 feet.
Equipment
- Digital Instant Read Thermometer
Ingredients
Shortbread
- 1 cup all-purpose flour, spooned and leveled
- ⅓ cup granulated sugar
- ½ tsp coarse Kosher salt (if using table salt, use half the amount)
- ½ tsp vanilla extract
- ½ cup cold unsalted butter, diced
Caramel
- ½ cup unsalted butter, melted
- ½ cup light corn syrup
- ½ cup granulated sugar
- ½ cup dark brown sugar, lightly packed
- ½ cup sweetened condensed milk
- ¼ tsp coarse Kosher salt (if using table salt, use half the amount)
- 2 tsp vanilla extract
Ganache
- 4 oz heavy whipping cream
- 4 oz good-quality dark or semi-sweet chocolate, chopped
- ¼ tsp flaky finishing salt, such as Maldon
Instructions
Shortbread
- Preheat the oven to 350 F. Line an 8×8 inch square baking dish with two sheets of parchment paper, so that they completely line the bottom and sides of the pan. Crease the paper at the top edges of the pan to help keep it in place.
- In a bowl, combine the flour, sugar, salt and vanilla. Add the butter and use a pastry cutter to cut the butter into the flour mixture until well incorporated, and the crumbs are moist and crumbly.Dump the dough crumbs into the prepared pan. Spread out evenly in the pan, then use your hands to press the crumbs down firmly against the bottom of the pan.
- Bake the crust on the center oven rack for 20 minutes, until pale golden brown.Set the pan on a cooling rack and cool for 20 minutes.(Don't start making the caramel until after you've cooled the shortbread, since the caramel cooks quickly.)
Caramel
- In a large microwave-safe bowl (I recommend a glass Pyrex bowl with a 2.5 quart capacity), whisk together the melted butter, corn syrup, granulated sugar, brown sugar, sweetened condensed milk and salt until smooth.
- Place the bowl in your microwave, uncovered. Microwave on high for 6 minutes, then stir and check the temperature with a digital instant read thermometer. The temperature of the caramel needs to reach between 238-242 degrees F.If the caramel isn't hot enough, continue to microwave on high in 15-second increments, checking the temperature each time until it reaches the correct temperature.My microwave is 1,000 watts, and it usually takes around 6 1/2 minutes.Note that if your microwave is a higher or lower wattage, it may take more or less time. Also, the temperature of your ingredients when you start can also affect how long it takes, but getting the caramel to the right temperature is the only thing that matters.
- Once the caramel reaches 238 degrees, take it out of the microwave, using oven mitts if the bowl is hot. Immediately stir in the vanilla until smooth; the caramel will bubble and hiss a little.
- Immediately pour the hot caramel over the cooled crust.Let the bars sit at room temperature to cool for 1 hour, then refrigerate until both the crust and the caramel are completely cooled and firm, about 1 – 1 1/2 hours.
Chocolate
- Set up a double boiler (a pan of simmering water with a heatproof bowl sitting on top of the pan – the bottom of the bowl should not touch the water).
- Measure the chocolate and cream into the bowl. Let the mixture warm until the chocolate melts, then stir the ganache with a spatula until smooth and shiny.
- Immediately pour the ganache over the cooled caramel, and smooth out the ganache.Let the bars sit at room temperature to let the ganache set for about 30 minutes, then refrigerate until the ganache is firm.
Cutting the Bars
- These bars are best eaten at room temperature when the caramel is soft and luscious. But when you cut the bars, you want them to be chilled and firm enough to cut cleanly, although not rock hard from the fridge.Once the ganache has set, take the bars out of the fridge. Lift the bars out of the pan by grabbing onto the parchment paper. Pull the paper away from the sides of the bars, and then slide the whole slab of bars off the paper and onto a cutting board.
- Press against the caramel around the edges. If it's soft enough that you can make an impression, then they're ready to be cut. You don't want to let them warm up enough that the caramel gets soft and gooey, or they will be hard to cut cleanly, and you'll need to chill them again before cutting.Use a large, sharp chef's knife to cut straight down, cutting the whole slab in half. Slide the knife out sideways, not back up through the bars. Then cut each half into 8 squares, for a total of 16 squares.To keep the bars looking neat, wipe the knife clean in between cuts.
- Before serving, sprinkle the bars with the flaky salt.
Heather, I made these for the neighbors for Xmas and they turned out wonderful! I was a little skeptical of that perfectly clean cut, but I followed all of your directions and they came out brilliant! Thanks!! Kim
I’ve made these a few times now and they are always amazing! My family now asks for these as a gift on holidays. The microwaved caramel is a game changer. Thank you for this recipe!