¼cup plus 2 tablespoons (42g)powdered sugar, siftedplus extra for sprinkling on top
1teaspoonbaking powder
¼teaspoonfine sea salt
¾cup (170g)unsalted butter, room temperature
Blueberry Filling
3 ½cups (454-510g)fresh blueberries*
1teaspoon lemon juice
½cup (100g)granulated sugar
2teaspoons cornstarch
Instructions
Crumb Topping
In a medium-sized bowl, whisk together the flour, brown sugar, granulated sugar, cinnamon and salt until well blended. Work the butter into the flour mixture with your fingertips, until it looks sandy, with no large pieces of butter remaining. Press the mixture together to form chunks. Set aside in the refrigerator until ready to use.
Crust
Preheat the oven to 350ºF (180ºC). Line an 8-inch square baking pan with parchment paper, leaving a couple of inches of overhang. These will be handles to lift the bars out of the pan.
In a medium-sized bowl, whisk together the flour, powdered sugar, baking powder and salt until well blended. In a large bowl, beat the butter until smooth. Add the flour mixture and beat just until combined.
Press the dough evenly into the baking pan. Bake until the surface looks light golden brown, about 20 minutes. Meanwhile, prepare the filling.
Blueberry Filling
In a large bowl, toss the blueberries with the lemon juice. Mix in the sugar and cornstarch. Pour the blueberry mixture over the warm crust. Top evenly with the crumb topping. Return the pan to the oven and continue baking until the topping is golden brown and the filling is bubbly, about 28-35 more minutes. Let cool completely before removing the bars from the pan. Sprinkle with powdered sugar.
Notes
*If you want to use frozen blueberries, they tend to be more watery. Rinse off any ice and make sure the berries are well-drained and patted dry with paper towels. Increase the cornstarch to 1 tablespoon.