01 - Whisk together all-purpose flour, baking powder, baking soda, and salt in a medium bowl.
02 - In a large mixing bowl, beat the softened butter and granulated sugar using an electric mixer until light and fluffy, about 2 to 3 minutes.
03 - Add the egg, vanilla extract, and sour cream to the creamed mixture. Beat until thoroughly combined.
04 - Gradually mix the dry ingredients into the wet mixture until just incorporated. Do not overmix.
05 - Cover the dough and refrigerate for at least 1 hour to firm up and make shaping easier.
06 - Preheat oven to 350°F. Line baking sheets with parchment paper.
07 - Scoop 2-tablespoon amounts of dough, shape into balls, and arrange 2 inches apart on the prepared baking sheets.
08 - Gently press each dough ball to 1/2-inch thickness using your palm or the bottom of a glass.
09 - Bake for 9 to 11 minutes, until edges just begin to turn golden. Avoid overbaking for a soft texture.
10 - Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
11 - Beat softened butter until creamy. Gradually add powdered sugar and blend. Mix in heavy cream, vanilla extract, and a pinch of salt until frosting becomes smooth and fluffy. Incorporate food coloring if desired.
12 - Spread a generous amount of frosting atop each cooled cookie. Decorate with sprinkles. Allow frosting to set before serving.