01 - Whisk together flour, baking powder, baking soda, and salt in a medium bowl. Set aside for later use.
02 - Beat softened butter and granulated sugar in a large mixing bowl until light and fluffy, approximately 2–3 minutes.
03 - Add egg and vanilla extract to the butter mixture, beating until fully incorporated. Mix in sour cream until smooth.
04 - Gradually incorporate dry ingredients into the wet mixture, mixing until a soft, cohesive dough forms.
05 - Divide dough in half, flatten into discs, wrap in plastic wrap, and refrigerate for minimum 1 hour.
06 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
07 - On lightly floured surface, roll dough to 1/4-inch thickness. Cut circles approximately 2.5 inches in diameter and place 2 inches apart on prepared baking sheets.
08 - Bake for 9–11 minutes until edges are set but not browned. Cool completely on wire rack.
09 - Beat softened butter until creamy. Gradually add sifted powdered sugar, beating thoroughly after each addition. Incorporate vanilla, salt, and cream. Beat on high speed for 2–3 minutes until fluffy. Add food coloring if desired.
10 - Spread or pipe frosting generously onto cooled cookies. Add sprinkles if desired.