01 - Preheat oven to 350°F. Line a 9×13-inch baking pan with parchment paper, allowing overhang for easy removal.
02 - Whisk together flour, baking powder, and salt in a medium bowl. Set aside.
03 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2-3 minutes.
04 - Mix in egg, egg yolk, vanilla extract, and almond extract until fully incorporated.
05 - Gradually add dry ingredients to wet mixture, mixing just until combined.
06 - Press dough evenly into prepared baking pan using spatula or fingers.
07 - Bake for 18-20 minutes until edges are lightly golden and center remains soft.
08 - Let bars cool in pan on wire rack to room temperature.
09 - Beat butter until creamy. Gradually blend in powdered sugar, milk, vanilla, and salt until fluffy and spreadable.
10 - Spread frosting evenly over cooled bars. Top with red, white, and blue sprinkles.
11 - Lift bars from pan using parchment overhang. Cut into 16 squares.