Preheat oven to 350F and line a 9X13 pan with parchment paper. *A 10x14 metal baking pan may also be used.
Combine melted butter and sugar in a large bowl and stir well.
(1 cup unsalted butter,1 ¼ cup brown sugar, ½ cup granulated sugar)
Add eggs, egg yolk, and vanilla extract and stir until completely combined. Set aside.
(2 large eggs + 1 egg yolk, 2 teaspoons vanilla extract)
In a separate bowl, whisk together flour, cornstarch, baking powder, and salt.
(2 ¼ cups all-purpose flour, 2 teaspoons cornstarch,½ teaspoon baking powder, 1 teaspoon salt)
Gradually stir dry ingredients into wet until completely combined.
Fold in white chocolate chips and strawberries, if using.
(1 cup white chocolate chips, 1 cup freeze-dried strawberries)
Spread blondie batter into prepared pan and transfer to oven.
Bake at 350F for 25-30 minutes or until a toothpick inserted in the center comes out clean or with a few fudgy crumbs.
Allow to cool before cutting and enjoying.