1. Preheat your oven to 350°F and line a 12-count cupcake pan with paper liners.

2. In a medium bowl, whisk together the cake flour, baking powder, baking soda, and salt.

3. In a large bowl, beat the butter and sugar until light and fluffy. Add the egg whites one at a time, then stir in the vanilla, milk, and sour cream until the mixture is smooth.

4. Gradually add the dry ingredients to the wet ingredients and mix until just combined, being careful not to overmix.

5. Divide the batter evenly among the prepared cupcake liners. Bake for 18–20 minutes, or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool completely before frosting.

6. Beat the unsalted butter until it’s creamy and smooth.

7. Gradually add the powdered sugar and 3 tablespoon of whole milk, beating until the frosting is smooth and creamy. If the frosting is too thick, add a bit more milk.

8. Stir in the pure vanilla extract until well combined.

9. If you’d like to achieve the signature Magnolia Bakery pink frosting, add a few drops of pink gel food coloring and mix until the desired shade is reached.