01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper and set aside.
02 - In a medium bowl, whisk together the flour, baking powder, and salt until well combined.
03 - In a large bowl, beat the softened butter and granulated sugar together until light and fluffy, approximately 2-3 minutes.
04 - Add the egg, vanilla extract, and almond extract if using. Mix until fully incorporated into the butter mixture.
05 - Gradually add the flour mixture to the wet ingredients, mixing just until the dough comes together and no dry streaks remain.
06 - Divide the dough evenly into 4-5 separate bowls. Add a small amount of different pastel gel food coloring to each bowl, mixing thoroughly until the color is uniform throughout.
07 - Using a tablespoon or cookie scoop, portion the colored dough into balls. Place the dough balls 2 inches apart on the prepared baking sheets.
08 - Gently flatten each dough ball slightly with the palm of your hand to ensure even baking.
09 - Bake for 10-12 minutes, or until the edges are set but the centers remain slightly soft. Take care not to overbake.
10 - Allow the cookies to cool on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely before filling.
11 - Beat the softened butter until creamy. Gradually add the powdered sugar, vanilla extract, salt, and milk. Beat until smooth and fluffy, adding additional milk if needed to achieve spreadable consistency.
12 - Once cookies are completely cool, pipe or spread a layer of buttercream onto the flat side of half the cookies. Top each filled cookie with a matching cookie to form sandwiches.
13 - If desired, roll the edges of the filled sandwiches in sprinkles for a festive finish.