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