20 servings
**Prep Time:** 15 minutes
**Total Time:** 1 hour 30 minutes
**Ingredients**
**Cookies**
– 2 1/3 cups all-purpose flour
– 2 tsp cornstarch
– 1 tsp kosher salt
– 1/2 tsp baking powder
– 1/4 tsp baking soda
– 1/2 cup unsalted butter, softened
– 1 cup granulated sugar
– 1 large egg, room temperature
– 2 tsp vanilla extract
– 1/2 cup sour cream, room temperature
**Frosting**
– 1/2 cup unsalted butter, softened
– 3 cups powdered sugar
– 2 tbsp milk
– 1 tsp vanilla extract
– 1/2 tsp kosher salt
– Liquid red food coloring
– Rainbow sprinkles, for decoration
**Directions**
1. In a medium bowl, whisk together flour, cornstarch, salt, baking powder, and baking soda.
2. Using a stand mixer with a paddle attachment, cream together butter and sugar until light and fluffy. Add egg and vanilla, beat until combined. Mix in sour cream.
3. Gradually add dry ingredients, mixing until combined. Shape dough into a disk, wrap in plastic, and chill for 1 hour.
4. Preheat oven to 375°F. Line baking sheets with parchment paper.
5. Roll out chilled dough on a floured surface, cut into heart shapes, and place on baking sheets.
6. Bake for 9-10 minutes, then cool on a rack.
**Frosting:**
1. Beat butter until creamy. Add powdered sugar, milk, vanilla, and salt until combined. Mix in red food coloring to reach a light pink color.
**Decoration:**
1. Frost cooled cookies and add rainbow sprinkles.
*Tip:* Only re-roll dough once to prevent cookies from shrinking.
