Preheat oven to 350°F.
In a large mixing bowl, whisk together the flour, white sugar, salt and baking powder until combined.
1 1/4 cup flour, 1/2 cup sugar, 1 tsp. salt, 1/2 tsp. baking powder
In another medium sized bowl, combine creamy peanut butter, brown sugar, eggs, butter, milk and vanilla extract until smooth.
1/3 cup peanut butter, creamy, 1/2 cup dark brown sugar, packed, 2 large eggs, lightly beaten, 1/4 cup butter, unsalted, melted and slightly cooled, 2 Tbsp. whole milk, 1 tsp. vanilla
Add peanut butter mixture to flour mixture and stir until combined with a rubber spatula.
Fold in chocolate chips.
1/2 cup semisweet chocolate chips
Spray a 9x9 inch aluminum square baking pan with baking spray.
Turn batter into pan and spread evenly. Top with chopped Reese's mini cup pieces over batter.
1/2 cup Reese's miniature cups, chopped (or more as desired to cover the top of the blondes prior to baking)
Bake for 19-20 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. (*Note: if baking in a glass pan, baking time will be increased).
Cool on a wire rack, cut and enjoy!