01 - Whisk together flour, baking powder, and salt in a medium bowl. Set aside for later use.
02 - Beat butter and granulated sugar on medium speed until light and fluffy, approximately 2-3 minutes.
03 - Add egg and vanilla extract to the butter mixture, mixing until thoroughly combined.
04 - Gradually incorporate dry ingredients into the wet mixture, mixing just until dough forms.
05 - Divide dough in half, flatten into discs, wrap in plastic, and refrigerate for minimum 30 minutes.
06 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
07 - On lightly floured surface, roll one dough disc to ¼ inch thickness. Cut rounds using 2-inch cookie cutter. Place 1 inch apart on prepared sheets.
08 - Bake for 8-10 minutes until edges barely begin to golden. Cool on sheets 2 minutes, then transfer to racks to cool completely.
09 - Beat butter until creamy. Gradually add powdered sugar, milk, vanilla, and salt, beating until smooth and fluffy consistency is achieved.
10 - Divide buttercream into small bowls and tint each with different pastel food coloring gel.
11 - Spread or pipe generous layer of buttercream onto flat side of half the cookies. Top with remaining cookies to form sandwiches.
12 - Allow assembled cookies to set for 20 minutes before serving.