01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Whisk together flour, baking powder, and salt in a medium bowl.
03 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2–3 minutes.
04 - Mix in the egg and vanilla extract until fully incorporated.
05 - Gradually blend dry ingredients into wet mixture, mixing until dough comes together.
06 - Divide dough in half, shape into flat disks, wrap in plastic, and refrigerate for 30 minutes.
07 - On lightly floured surface, roll dough to 1/4-inch thickness. Cut with round or flower-shaped cutters.
08 - Arrange cookies 2 inches apart on prepared sheets. Bake 10–12 minutes until edges turn golden.
09 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool entirely.
10 - Beat butter until smooth and creamy. Gradually incorporate sifted confectioners sugar, mixing thoroughly.
11 - Add milk, vanilla, and salt. Whip 2–3 minutes until fluffy. Add additional milk 1 tsp at a time if needed for piping consistency.
12 - Divide buttercream among separate bowls. Tint each portion with gel food coloring as desired.
13 - Fit piping bags with small star, petal, and leaf tips. Fill bags with colored buttercream.
14 - Pipe flower and leaf decorations onto completely cooled cookies using prepared piping tips.
15 - Allow decorated cookies to rest at room temperature until buttercream firms slightly.