01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Whisk together flour, baking powder, and salt in a medium bowl until well blended.
03 - Beat butter and sugar in a large bowl until light and fluffy, about 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.
06 - Divide dough evenly into 4-5 bowls. Tint each with a different pastel gel food coloring, mixing until uniform color is achieved.
07 - Scoop dough into tablespoon-sized balls and place 2 inches apart on prepared baking sheets.
08 - Gently press each ball with palm to flatten slightly for even baking.
09 - Bake for 10-12 minutes until edges are set but centers remain soft. Avoid overbaking.
10 - Let cookies rest on trays for 5 minutes, then transfer to wire rack to cool completely.
11 - Beat butter until creamy. Add powdered sugar, vanilla, salt, and milk. Whip until smooth and fluffy, adjusting consistency with additional milk if needed.
12 - Pipe or spread buttercream onto flat side of half the cookies. Top each with matching cookie to form sandwiches.
13 - Roll edges in sprinkles if desired for decorative finish.