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, cream the butter and sugar using a hand mixer or stand mixer until light and fluffy, about 3 minutes.
04 - Beat in the egg and vanilla extract until fully combined and smooth.
05 - Gradually add the dry ingredients to the wet mixture, mixing on low speed just until the dough comes together. Do not overmix.
06 - Divide dough into two equal discs, wrap tightly in plastic wrap, and refrigerate for at least 30 minutes.
07 - On a lightly floured surface, roll out dough to 1/4-inch thickness. Use a bunny-shaped cookie cutter to cut out cookies and place them 2 inches apart on prepared baking sheets.
08 - Bake for 8 to 10 minutes, or until edges are just beginning to turn golden. Let cool completely on a wire rack before frosting.
09 - Beat softened butter until creamy. Gradually add powdered sugar, milk, and vanilla, beating until smooth and spreadable. Tint portions with food coloring as desired.
10 - Frost cooled cookies with buttercream using piping bags or spatulas. Decorate with candy eyes or sprinkles to create bunny faces if desired. Allow frosting to set before serving.