Add flour, baking powder, and salt. Stir until just incorporated.
3 cups sifted all-purpose flour, 1 teaspoon baking powder, ½ teaspoon salt
Add batter to the prepared pan.
Bake for about 15-20 minutes, or until the edges are very light golden brown. A toothpick inserted into the center should come out clean. It's better to slightly underbake the bars than to overbake them.
Let the bars cool in the pan until they reach room temperature.
To prepare frosting, beat butter until fluffy.
1 cup salted butter
Add powdered sugar, and mix until combined.
3 cups powdered sugar
Stir in vanilla extract.
2 teaspoons vanilla extract
Mix in enough cream to make a spreadable frosting.
2-3 tablespoons heavy cream
Spread the frosting over the cooled bars and top with sprinkles.
Red, white, and blue sprinkles
Notes
Butter: If using unsalted butter, increase the salt to 1 teaspoon.
Brown sugar: I use light brown sugar in this recipe.
Almond extract: Almond extract adds a nice depth of flavor and more of that classic bakery-type flavor. However, you can omit it if needed.
Flour: It's import to properly measure the flour to avoid dry, heavy, or crumbly bars. To properly measure either weigh the flour (click "metric" just above the ingredients) or sift, lightly spoon into a measuring cup, and level.