Preheat oven to 350°F. Line two cookie sheets with parchment paper.

Mix butter, sugar, and sour cream in a mixer until smooth. Add egg, baking soda, baking powder, salt, and vanilla. Mix in flour until dough forms.

Scoop two tablespoons of dough per cookie onto parchment sheets, 2 inches apart. Press flat with the bottom of a glass sprayed with nonstick spray.

Bake for 7-9 minutes until edges are light golden. Do not overbake.

Make frosting by combining butter and powdered sugar, then add vanilla, salt, and milk. Tint with food coloring if desired.

Frost cooled cookies with about 1 tablespoon of frosting. Decorate with sprinkles.

Store in an airtight container for up to 3 days.