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