01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together flour, baking powder, and salt until well blended.
03 - In a large bowl, beat butter and granulated sugar together until light and fluffy, about 2-3 minutes.
04 - Add egg, vanilla extract, and almond extract if using. Mix 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 portion with a different pastel gel food coloring, mixing until uniform color is achieved.
07 - Using a tablespoon or cookie scoop, portion dough into balls. Place 2 inches apart on prepared baking sheets. Flatten each ball slightly with palm.
08 - Bake for 10-12 minutes until edges are set but centers remain soft. Do not overbake.
09 - Let cookies cool on trays for 5 minutes, then transfer to wire rack to cool completely before filling.
10 - Beat butter until creamy. Add powdered sugar, vanilla, salt, and milk. Beat until smooth and fluffy. Adjust consistency with additional milk if needed.
11 - Pipe or spread buttercream onto flat side of half the cookies. Top each with matching cookie to form sandwiches. Roll edges in sprinkles if desired.