Preheat the oven to 350°F. Line a standard 12-cup muffin pan with paper liners. Set aside.

In a large mixing bowl use a whisk to sift the flour, sugar, baking powder, baking soda and salt together. Set aside.

In a separate medium bowl, whisk the melted butter, sour cream, buttermilk, vanilla extract and egg whites until fully combined.

Pour the wet mixture into the flour mixture and stir together until everything is combined and no flour streaks remain.

Fold the sprinkles into the batter. Try to mix as little as possible to keep the colors of the sprinkles from running together in the batter.

Use a large ice cream scoop or ¼ cup measuring cup to fill the wells of the cupcakes pan ¾ full.

Bake for 15-18 minutes. The edges of the cupcakes will be golden brown and a toothpick inserted into the center comes back clean. The middle of the cupcakes should bounce back when gently pressed.

Cool in the pan for 5 minutes before removing them to a cooling rack to cool completely.

Once the cupcakes are cooled, frost each one with your vanilla buttercream (OR your favorite frosting) and garnish with sprinkles.

Chill until serving.