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 combined.
03 - In a large bowl, beat butter and granulated sugar together until light and fluffy, approximately 2–3 minutes.
04 - Beat in the egg and vanilla extract until fully incorporated into the mixture.
05 - Gradually add dry ingredients to wet ingredients, mixing until dough just comes together.
06 - Divide dough in half, flatten into disks, wrap in plastic wrap, and refrigerate for 30 minutes.
07 - On a lightly floured surface, roll dough to 1/4-inch thickness. Cut with round or flower-shaped cookie cutters.
08 - Place cookies 2 inches apart on prepared baking sheets. Bake for 10–12 minutes until edges are just golden.
09 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool completely.
10 - Beat butter until smooth and creamy. Gradually add sifted confectioners sugar, mixing thoroughly after each addition.
11 - Add milk, vanilla, and salt. Beat for 2–3 minutes until fluffy. Add additional milk 1 tsp at a time if needed for piping consistency.
12 - Divide buttercream into separate bowls and tint with gel food coloring to achieve desired colors.
13 - Fit piping bags with small star, petal, and leaf tips. Fill bags with colored buttercream.
14 - Pipe flowers and leaves onto completely cooled cookies using various piping tips.
15 - Allow decorated cookies to rest at room temperature until buttercream firms slightly before serving or storing.