01 - Preheat oven to 350°F. Line a 9x13 inch baking pan with parchment paper, allowing overhang for easy removal.
02 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2-3 minutes.
03 - Incorporate eggs one at a time, mixing thoroughly after each addition. Blend in vanilla extract.
04 - Whisk together flour, baking powder, and salt in a separate bowl.
05 - Gradually add dry ingredients to the wet mixture, mixing just until incorporated.
06 - Press dough evenly into prepared pan. Bake for 18-22 minutes until edges are lightly golden and center remains soft.
07 - Allow bars to cool fully in the pan on a wire rack before frosting.
08 - Beat butter until creamy. Blend in powdered sugar, then add milk and vanilla extract until smooth. Add food coloring if desired.
09 - Spread frosting evenly over cooled bars. Add sprinkles if using. Lift from pan using parchment overhang, cut into squares, and serve.