1. Preheat the oven to 350°F and line two baking sheets with parchment paper.

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

3. Add the egg, vanilla extract, and milk, then mix until smooth.

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

5. Gradually add the dry ingredients to the wet ingredients and mix until a soft dough forms.

6. Divide the dough into separate bowls and tint each portion with pastel food coloring.

7. Scoop the dough into 1-inch balls and roll each one in sanding sugar.

8. Place the dough balls on the prepared baking sheets about 2 inches apart.

9. Bake for 8 to 10 minutes, until the cookies are puffed and set but not browned.

10. Remove from the oven and immediately press a chocolate kiss into the center of each cookie.

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