01 - Preheat oven to 350°F. Line two baking sheets with parchment paper and set aside.
02 - In a medium bowl, whisk together flour, baking powder, and salt until well blended.
03 - In a large bowl, beat softened butter and granulated sugar with an electric mixer on medium speed until light and fluffy, approximately 3 minutes.
04 - Add egg and vanilla extract to butter mixture. Beat until fully combined, scraping down bowl sides as needed.
05 - Gradually add dry ingredients to wet mixture, mixing on low speed just until dough forms. Do not overmix.
06 - Divide dough into two equal portions, shape into discs, and wrap tightly in plastic wrap. Refrigerate for at least 30 minutes.
07 - On a lightly floured surface, roll dough to 1/4-inch thickness. Using a bunny-shaped cookie cutter, cut out cookies and arrange 2 inches apart on prepared baking sheets.
08 - Bake for 8 to 10 minutes, or until edges begin to turn golden. Remove from oven and let cool completely on wire racks before frosting.
09 - While cookies cool, beat softened butter until creamy. Gradually incorporate powdered sugar, milk, and vanilla extract, continuing to beat until smooth and spreadable. Divide and tint portions with food coloring if desired.
10 - Frost cooled cookies with buttercream using piping bags or offset spatulas. Add candy eyes or sprinkles to create bunny faces. Allow frosting to set before serving.