1. In a medium bowl, whisk together flour, baking powder, baking soda, and salt.

2. In a large mixing bowl, cream the butter and sugar until light and fluffy.

3. Beat in the eggs one at a time, then add vanilla and sour cream. Mix until smooth.

4. Gradually add the dry ingredients, mixing just until combined. Do not overmix.

5. Cover and refrigerate the dough for at least 1 hour.

6. Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.

7. Scoop about 2 tablespoons of dough, roll into balls, and flatten slightly on the baking sheet.

8. Bake for 9–11 minutes. Cookies should remain pale with set edges.

9. Let cookies cool completely on a wire rack.

10. For the frosting, beat softened butter until creamy. Gradually add powdered sugar.

11. Add milk or cream and vanilla extract. Beat until light and fluffy. Add food coloring if desired.

12. Frost cooled cookies and decorate with sprinkles immediately.

13. Store in an airtight container at room temperature for up to 3 days or refrigerate for longer freshness.