1. Preheat the oven to 350°F. Line baking sheets with parchment paper.

2. In a large mixing bowl, beat 1 cup softened butter with the granulated sugar until light and fluffy.

3. Add the eggs and 2 teaspoons vanilla extract, then mix until smooth and fully combined.

4. In a separate bowl, whisk together the flour, baking powder, and salt.

5. Gradually add the dry ingredients to the wet ingredients, then mix in 2 tablespoons milk until a soft dough forms.

6. Scoop the dough into evenly sized portions and place them on the prepared baking sheets, leaving space between each cookie.

7. Gently flatten each dough ball slightly with your hand or the bottom of a glass.

8. Bake for 9 to 11 minutes, just until the tops are set and the edges are very lightly golden.

9. Let the cookies cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.

10. To make the frosting, beat 1/2 cup softened butter with the powdered sugar, 2 tablespoons milk, and 1 teaspoon vanilla extract until fluffy and smooth.

11. Add a few drops of food coloring if desired and mix until the frosting reaches your preferred color.

12. Spread the frosting over the cooled cookies and top with rainbow sprinkles.

13. Let the frosting set before serving or stacking.