Cream the Butter and Sugar: In a large mixing bowl, beat softened butter and sugar together until light and fluffy, about 2–3 minutes.
Add Wet Ingredients: Mix in the egg and vanilla extract until fully incorporated.
Combine Dry Ingredients: In a separate bowl, whisk together flour, baking powder, and salt. Gradually add to the wet mixture until a soft dough forms.
Chill the Dough: Divide dough into two portions, wrap each in plastic wrap, and chill for at least 30 minutes.
Preheat Oven: Set oven to 350°F (175°C). Line baking sheets with parchment paper.
Roll and Cut: On a lightly floured surface, roll dough to about ¼-inch thickness. Use leaf-shaped cookie cutters to cut out cookies.
Bake: Transfer cookies to baking sheets and bake for 8–10 minutes, or until edges are just starting to turn golden.
Cool Completely: Let cookies rest for 5 minutes on the pan, then move to a wire rack to cool fully before decorating.