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 blended.
03 - In a large bowl, beat butter and sugar with electric mixer until light and fluffy, about 3 minutes.
04 - Beat in egg and vanilla extract until fully incorporated.
05 - Gradually add dry ingredients to wet mixture, mixing just until dough comes together. Avoid overmixing.
06 - Divide dough into two discs, wrap in plastic, and refrigerate for at least 30 minutes.
07 - On lightly floured surface, roll dough to 1/4-inch thickness. Cut with bunny-shaped cookie cutter and place 2 inches apart on prepared sheets.
08 - Bake for 8 to 10 minutes until edges just begin to turn golden. Cool completely on wire rack.
09 - Beat softened butter until creamy. Gradually add powdered sugar, milk, and vanilla, beating until smooth and spreadable. Tint with food coloring if desired.
10 - Frost cooled cookies with buttercream using piping bags or spatulas. Add candy eyes or sprinkles for bunny faces. Let frosting set before serving.