This delicious Harry Potter inspired dessert pairs sweet and tart rhubarb crumble topped with buttery cinnamon oat streusel and creamy vanilla bean custard. The salty sweet crumble with the tart fruit filling and rich custard makes the most fantastic combination of flavors and textures. You’ll love this easy fruit crumble recipe!
Looking for more rhubarb recipes? Don’t miss this bourbon peach cobbler, maple apple cobbler, and rhubarb oatmeal bars.
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When to Find Rhubarb
Early spring is the best season for fresh rhubarb, so watch for it in your local grocery store or farmer’s market between April and June. And if you can’t find it fresh, you may be able to get bags of frozen rhubarb.
Other Ways to Use Rhubarb
In the summer, I make rhubarb jam, pies, tarts, oatmeal bars, upside down cakes and even ice cream and homemade liqueur with our fresh rhubarb. I often pair it with strawberries, apples, or blueberries, and freeze the rest to use throughout the winter.
Why You’ll Love This Recipe
A fruit crisp, crumble or cobbler is much easier to make than pie. Simply stir together the filling ingredients, sprinkle over the crumble topping, and bake. And while all my recipes are high altitude tested, this one will work at any altitude.
See the recipe card at the end of the post for the full ingredients list and instructions.
Ingredients
Rhubarb Crumble
- Rhubarb. Rhubarb is extremely tart, making it an excellent ingredient for sweet desserts. It breaks down and thickens into a jammy consistency when cooked.
- Granulated Sugar + Brown Sugar. Granulated sugar in the filling sweetens the rhubarb, while brown sugar in the crumble topping adds a delicious rich flavor.
- All-purpose Flour. Most of the flour will go into the crumb topping, but a little flour helps to thicken the rhubarb filling.
- Lemon Zest. Enhances the flavor of the rhubarb.
- Baking Soda. Neutralizes the acidity and tartness of the rhubarb.
- Cinnamon. Complements all the flavors in the crumble.
- Oats. Adds texture and crunch in the topping.
- Coarse Kosher Salt. Balances the sweetness.
- Unsalted Butter. Moistens the crumb topping and helps it to bake up crisp.
Vanilla Bean Custard
- Whole Milk + Cream. A combination of milk and cream makes the custard rich, creamy and luxurious.
- Granulated Sugar. Adds sweetness.
- Egg Yolks. The egg yolks add richness, as well as help to thicken the custard a little.
- Corn Starch. Thickens the custard.
- Coarse Kosher Salt. Balances the sweetness and enhances the flavor.
- Vanilla. If you can, use real vanilla beans. The black specks look gorgeous, and the flavor is incredible. You could also use vanilla bean paste or good-quality vanilla extract.
- Unsalted Butter. A touch of butter added at the end adds extra richness and flavor.
Instructions
Custard
- In a saucepan whisk together the sugar, salt and cornstarch. Add the egg yolks, vanilla bean, and a small amount of milk, whisking until smooth. Whisk in the rest of the milk and cream.
- Over medium heat, cook the custard, while whisking constantly, until thickened enough to coat the back of a spoon. Remove from the heat and whisk in the butter.
- Cover the custard with plastic wrap, resting right against the surface, and refrigerate until needed. Stir the custard until smooth before serving with the rhubarb crumble.
- The custard can be served warm, but I prefer it chilled. The cool, creamy custard spooned over the hot crumble is lovely.
The English serve up custard more frequently than would occur to me to do, because really, when have you ever been served a side of custard with your cake or fruit crumble or pie instead of ice cream or whipped cream? Since custard has similar ingredients to ice cream, it really does pair perfectly with anything that you might top with a scoop of ice cream.
Filling
- Preheat the oven to 350F, and position a rack in the center of the oven. Brush a deep dish pie pan or a 9 or 10-inch baking dish with the softened butter.
- Toss the rest of the filling ingredients together and spread into the pan. Bake for 10 minutes while you make the crumble topping.
Topping
- In a bowl (I just use the same one I mixed the filling in), combine the flour, brown sugar, oats, cinnamon and salt. Drizzle with the melted butter and stir until moistened and crumbly.
- Remove the pan from the oven, and stir up the filling. Sprinkle the topping over the rhubarb.
- Return the pan to the oven, and bake for 40-45 minutes, until the filling is bubbling and the topping is golden brown.
Serving
- Cool the rhubarb crumble for about 30 minutes.
- Serve scoops of the warm crumble, with cool and creamy custard on the side.
Be sure to read all of my BAKING FAQs where I discuss ingredients, substitutions and common baking questions, so that you can be successful in your own baking!
Frequently Asked Questions
Either fresh or frozen rhubarb will work, depending on what’s available at your local grocery store or farmer’s market. You’ll typically find fresh rhubarb between April and June. If using frozen, you’ll need to let it thaw first, or it will affect the baking time.
Yes, the green leaves are inedible due to their high concentration of oxalic acid, and consuming the leaves can cause rhubarb leaf poisoning. They are not toxic to the touch, though, so simply trim the leaves off the stalks and discard.
Baking soda neutralizes acid. When combined with rhubarb, it helps to neutralize some of the acidity and bitterness of the rhubarb, so that you don’t need to use as much sugar to sweeten the rhubarb.
You certainly can! Strawberry rhubarb is a classic combination, but peaches, blueberries and cherries are also delicious with rhubarb. If you add strawberries or peaches to your crumble, you’ll need to increase the flour in the filling by a few more tablespoons to thicken your filling, since those fruits contain more water. Apple rhubarb crumble is also wonderful.
The main difference between a crisp and a crumble is in the streusel topping. Traditionally, crisps contain oats and crumbles do not. In a crisp recipe, the oats in the topping crisp up as the topping bakes, hence the name. Over time, though, the terms crumble and crisp have been used interchangeably, and the difference is negligible. My crumble topping recipe contains oats, and there you have it.
Rhubarb crumble is best served warm, the day it’s made, but it still tastes great the next day, even cold. Leftovers should be covered and refrigerated, and eaten within 2 days.
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Rhubarb Crumble and Custard
All recipes on Curly Girl Kitchen are developed for high altitude at 5,280 feet. See FAQs for adjusting to higher or lower elevations.
Ingredients
Vanilla Bean Custard
- ¼ cup granulated sugar
- ⅛ tsp coarse Kosher salt (if using table salt, use half the amount)
- 2 tbsp corn starch
- 3 egg yolks
- ½ vanilla bean, seeds scraped (or 1/2 tsp vanilla bean paste)
- 1 ¼ cups whole milk
- ¼ cup heavy whipping cream
- 2 tbsp unsalted butter
Rhubarb Filling
- ½ tbsp unsalted butter, softened
- 1 ½ lbs fresh rhubarb (or frozen and thawed), cut into 1/2 inch pieces
- ½ cup granulated sugar
- 1 tbsp all-purpose flour
- 1 tsp fresh lemon zest
- ¼ tsp baking soda
- ¼ tsp ground cinnamon
Crumb Topping
- 1 cup all-purpose flour, fluffed, spooned and leveled
- ¾ cup light or dark brown sugar, lightly packed
- ½ cup old-fashioned rolled oats
- ½ tsp ground cinnamon
- ½ tsp coarse Kosher salt (if using table salt, use half the amount)
- 4 tbsp unsalted butter, melted
Instructions
Custard
- In a saucepan whisk together the sugar, salt and cornstarch. Add the egg yolks, vanilla bean, and a small amount of milk, whisking until smooth. Whisk in the rest of the milk and cream.
- Over medium heat, cook the custard, while whisking constantly, until thickened enough to coat the back of a spoon. Remove from the heat and whisk in the butter.
- The custard can be served warm, but I prefer it chilled. The cool, creamy custard spooned over the hot crumble is lovely.
- Cover the custard with plastic wrap, resting right against the surface, and refrigerate until needed. Stir the custard until smooth before serving with the rhubarb crumble.
Filling
- Preheat the oven to 350F, and position a rack in the center of the oven. Brush a deep dish pie pan or a 9 or 10-inch baking dish with the softened butter.
- Toss the rest of the filling ingredients together and spread into the pan. Bake for 10 minutes while you make the crumble topping.
Topping
- In a bowl (I just use the same one I mixed the filling in), combine the flour, brown sugar, oats, cinnamon and salt. Drizzle with the melted butter and stir until moistened and crumbly.
- Remove the pan from the oven, and stir up the filling. Sprinkle the topping over the rhubarb.
- Return the pan to the oven, and bake for 40-45 minutes, until the filling is bubbling and the topping is golden brown.
Serving
- Cool the rhubarb crumble for about 30 minutes.
- Serve scoops of the warm crumble, with cool and creamy custard on the side.
Notes
- Rhubarb crumble is best served warm, the day it’s made, but it still tastes good the next day, even cold. Leftovers should be covered and refrigerated, and eaten within 2 days.
- Refrigerate the leftover custard and eat within 1 week.
- Recipe is adapted from The Unofficial Harry Potter Cookbook.
Delicious! I was given some rhubarb and didn’t know what to do with it because I never buy it left to my own devices. I found Curly Girl’s recipe and thought I’d give it a shot. I baked it up, took it to my square dance club, and it was gone in a flash. I managed to grab some for myself before it was all gone. I was surprised at how good it was (I thought I didn’t like rhubarb)! I did make one alteration – I doubled the butter in the crumbled. I told some people that it was Curly Girl’s recipe, and they said they’ve heard of her 🙂
I’m so glad everyone loved it!
I’m so happy everyone loved it. 🙂
Delish! My son made this, followed directions and everyone wanted the recipe.
Thanks! Kristen
I’m so happy your family loved it!
Delicious! I used raspberries from the garden and took it to a pot luck. It was very popular 🙂
That sounds great with the raspberries!