Oh, do I love a good crumb bar with fruit filling, and these blueberry crumb bars are just fantastic. Brown butter gives the crust and crumb topping a rich, nutty flavor that’s simply incredible. The blueberry filling is sweet, thick and jammy, spiced with vanilla and nutmeg. I’ve even made these with a little almond flour in the crumble, which is also so good with the brown butter and blueberries. These blueberry crumb bars are as delicious as a blueberry crumb pie, but so much easier!
You might also love these peach crumb bars, rhubarb oatmeal bars, and cranberry almond crumb bars.
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Ingredients
Filling
- Blueberries. I like to use frozen blueberries for baking blueberry pies and crumbles, since they’re generally more affordable than fresh blueberries.
- Granulated Sugar. Sweetens the filling.
- Corn Starch. Thickens the filling to a consistency like blueberry jam.
- Nutmeg + Vanilla Extract. Flavor.
Crust and Crumble Topping
- Unsalted Butter. Browning the butter before making the dough gives the crust the most deliciously rich, nutty flavor. The butter also makes the crust and topping crisp.
- All-Purpose Flour. Gives the dough strength and structure.
- Dark Brown Sugar. Sweetness.
- Coarse Kosher Salt. Balances the sweetness for the perfect salty sweet flavor.
- Baking Powder. Gives the dough a bit of lift as it bakes.
See the recipe card at the end of the post for the full ingredients list and instructions.
Instructions
Filling
- Combine all the filling ingredients in a saucepan. Over medium heat, bring the mixture to a boil, while stirring frequently. Once it starts to thicken and bubble, stir constantly and cook for another 30-60 seconds.
- Set the filling aside to cool slightly while you make the crust and crumble topping.
Crust and Crumble Topping
- Preheat the oven to 350. Line an 8×8 inch square baking pan with parchment paper.
- In a small saucepan, melt the butter over medium heat. Continue to cook the butter, swirling the pan occasionally, until nutty brown solids form on the bottom of the pan. This should take about 5 minutes.
- Meanwhile, in a bowl, combine 2 cups of the flour (reserving 1/2 cup of flour for later) with the brown sugar, salt and baking powder.
- As soon as the butter is browned, use a spatula to scrape the bottom of the pan to scrape up all the browned bits. Pour the hot butter over the flour mixture. Stir with a spoon to form it into a soft dough.
- Scoop 2/3 of the dough (reserving 1/3 of the dough for the crumb topping) into the prepared baking pan, and use your hands to press the dough evenly into the bottom of the pan. Bake for 20 minutes.
- Take the reserved 1/2 cup of flour and add it to the remaining 1/3 dough. Use a fork or pastry cutter to work the flour into the dough until you have a crumbly topping. Set aside.
- After the crust bakes for 20 minutes, take the pan out of the oven. Pour the blueberry filling over the hot crust, then sprinkle the blueberries with the crumb topping. Bake for another 30 minutes, until the filling is bubbling and the topping is golden brown.
- Cool completely before cutting into squares.
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
Why do you brown the butter first?
When you brown butter, the milk solids in the butter fall to the bottom of the pan, where they turn golden brown and develop a richer, nuttier flavor. The depth of flavor browned butter adds to baked goods is incredible.
How long do these bars stay fresh?
Store the bars in an airtight container, and they will stay fresh for up to 3 days.
Should I use fresh or frozen blueberries?
You can use either, but frozen blueberries are a great, inexpensive option for baking.
What other spices can I add to these?
I add nutmeg and vanilla to the blueberry filling, but you can also try cinnamon, cloves or cardamom. I also love substituting 1/2 – 1 cup of the all purpose flour with almond flour.
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Brown Butter Blueberry Crumb Bars
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
Filling
- 1 lb frozen blueberries, thawed
- ¼ cup granulated sugar
- 1 ½ tbsp corn starch
- ¼ tsp ground nutmeg, optional
- 1 tsp vanilla extract
Crust and Crumble Topping
- ¾ cup unsalted butter
- 2 ½ cups all-purpose flour, spooned and leveled, divided
- ⅓ cup light or dark brown sugar, lightly packed
- 1 tsp coarse Kosher salt (if using table salt, use half the amount)
- 1 tsp baking powder
Instructions
Filling
- Combine all the filling ingredients in a saucepan. Over medium heat, bring the mixture to a boil, while stirring frequently. Once it starts to thicken and bubble, stir constantly and cook for another 30-60 seconds.
- Set the filling aside to cool slightly while you make the crust and crumble topping.
Crust and Crumble Topping
- Preheat the oven to 350. Line an 8×8 inch square baking pan with parchment paper.
- In a small saucepan, melt the butter over medium heat. Continue to cook the butter, swirling the pan occasionally, until nutty brown solids form on the bottom of the pan. This should take about 5 minutes.
- Meanwhile, in a bowl, combine 2 cups of the flour (reserving 1/2 cup of flour for later) with the brown sugar, salt and baking powder.
- As soon as the butter is browned, use a spatula to scrape the bottom of the pan to scrape up all the browned bits. Pour the hot butter over the flour mixture. Stir with a spoon to form it into a soft dough.
- Scoop 2/3 of the dough (reserving 1/3 of the dough for the crumb topping) into the prepared baking pan, and use your hands to press the dough evenly into the bottom of the pan. Bake for 20 minutes.
- Take the reserved 1/2 cup of flour and add it to the remaining 1/3 dough. Use a fork or pastry cutter to work the flour into the dough until you have a crumbly topping. Set aside.
- After the crust bakes for 20 minutes, take the pan out of the oven. Pour the blueberry filling over the hot crust, then sprinkle the blueberries with the crumb topping. Bake for another 30 minutes, until the filling is bubbling and the topping is golden brown.
- Cool completely before cutting into squares.
How do you recommend storing this after its baked? How long does it stay good for?
Store the bars in an airtight container, and they will stay fresh for up to 3 days.