These blueberry bars are bursting with berry flavor and the perfect summer treat. Banana replaces half of the butter called for in traditional crumb bar recipes, but these blueberry bars taste so moist and indulgent, you'll never want to make them any other way. Feel free to use frozen, thawed blueberries (just pat them dry) and swap other berry jams in place of the raspberry.
Place rack in the center of oven and preheat the oven to 350 degrees. Lightly coat an 8x8-inch dish with cooking spray. Set aside.
In a small bowl, combine 1/4 cup sugar, cornstarch, and lemon juice. Stir in blueberries. Set aside.
Place the butter and remaining 3/4 cup sugar in the bowl of an electric mixer fitted with the paddle attachment or a large mixing bowl. Beat on medium speed just until combined. With the mixer on low, add the banana and vanilla. In a separate bowl, stir together the white whole wheat flour, all purpose flour, and salt. With the mixer on low, slowly add the dry ingredients to the butter mixture, mixing until it almost comes together in a ball.
Lightly and evenly pat two-thirds of the dough into the bottom and 1/4 up the sides of the preppared baking pan. Spread jam over the top of the dough. Drain blueberries of any excess liquid, then sprinkle the berries over the top. With your fingers, mix the oats and almonds into the remaining dough to create the topping. Break the topping into pieces and crumble it over the blueberries, covering most of the surface but leaving some blueberries exposed. Bake for 35 to 40 minutes, until lightly browned. Let cool completely and cut into bars.