• Preheat your oven to 350°F and grease or line an 8x8 inch baking pan with parchment paper.

Make the blueberry topping

• In a medium saucepan, add the blueberries, cornstarch, granulated sugar, lemon juice, lemon zest, and water and mix to combine.
  1 cup frozen wild blueberries, 1 tablespoon cornstarch, 1 tablespoon water, 1 & 1/2 tablespoon granulated sugar, 2 tablespoon lemon juice, zest of 1 lemon
• Cook over medium heat mixing from time to time until the blueberries become jammy and thick. Transfer to a bowl and allow to cool completely.

Make the Streusel topping

• In a small bowl, mix the flour, granulated sugar, brown sugar, cinnamon, and salt for the streusel topping.
  1/3 cup all-purpose flour, 2 tablespoons brown sugar, 2 tablespoons granulated sugar, 1/4 teaspoon ground cinnamon, Pinch of salt
• Pour the melted butter over the dry ingredients and mix with a fork until crumbly. Place the streusel bowl in the fridge while you make the blondie base.
  3 tablespoons unsalted butter

Make the blondie base

• In a medium bowl, cream the butter, granulated sugar, and brown sugar until well combined.
  1/2 cup unsalted butter, 1/2 cup light brown sugar, 1/2 cup granulated sugar
• Add the egg and vanilla extract, and mix until smooth.
  1 large egg, 1 teaspoon vanilla extract
• Add in the flour, cornstarch, baking powder, baking soda, and salt and mix just until a soft cookie dough forms.
  1 &1/2 cup all-purpose flour, 1/4 teaspoon baking powder, 1/8 teaspoon baking soda, 1/4 teaspoon salt, 1/2 tablespoon cornstarch
• Spread the blondie batter evenly into the prepared pan. Spread the blueberry jam on top, then top with the streusel and bake in the preheated oven.
• Bake for 40 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out clean.
• Allow to cool completely before adding a dusting of powdered sugar if desired then slicing them into squares.