01 - Preheat oven to 350°F. Line a 9×13-inch baking pan with parchment paper, leaving overhang for easy removal.
02 - In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
03 - In a large bowl, beat softened butter and sugar together until light and fluffy, about 2-3 minutes.
04 - Beat in egg, egg yolk, vanilla, and almond extract until fully combined.
05 - Gradually add flour mixture to wet ingredients, mixing until just combined.
06 - Evenly spread dough in prepared baking pan using a spatula or your fingers.
07 - Bake for 18-20 minutes until edges are lightly golden but center remains soft.
08 - Let bars cool completely in the pan on a wire rack.
09 - Beat butter until creamy. Gradually add powdered sugar, milk, vanilla, and salt, beating until fluffy and spreadable.
10 - Spread frosting evenly over cooled bars. Decorate with red, white, and blue sprinkles.
11 - Use parchment overhang to lift bars from pan. Cut into 16 squares and serve.