01 - Preheat oven to 350°F and line two baking sheets with parchment paper.
02 - Whisk together flour, baking powder, and salt in a medium bowl until well blended.
03 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2-3 minutes.
04 - Mix in egg, vanilla extract, and almond extract until fully incorporated.
05 - Gradually add flour mixture to wet ingredients, mixing just until dough comes together. Do not overmix.
06 - Divide dough evenly into 4-5 bowls. Tint each with a different pastel gel food coloring, mixing until color is uniform throughout.
07 - Scoop tablespoon-sized portions of dough and place 2 inches apart on prepared baking sheets.
08 - Flatten each dough ball slightly with palm. Bake for 10-12 minutes until edges are set but centers remain soft.
09 - Let cookies rest on baking sheets for 5 minutes, then transfer to wire rack to cool entirely before filling.
10 - Beat butter until creamy. Blend in powdered sugar, vanilla, salt, and milk until smooth and fluffy. Adjust consistency with additional milk if needed.
11 - Spread or pipe buttercream onto flat side of half the cookies. Top with remaining cookies to form sandwiches. Roll edges in sprinkles if desired.