Preheat oven to 350°F. Line muffin pans with 14-16 cupcake liners.

With an electric mixer, beat 2 egg whites on high speed in a medium bowl until soft peaks form, about 2-3 minutes. They should be light and fluffy.

In a separate bowl, whisk the flour, baking powder, and salt together. Set aside.

Using a handheld or stand mixer fitted with a paddle attachment beat the butter on high speed until smooth and creamy.

Add the sugar and beat on high speed for 2-3 minutes, scraping down the sides of the bowl with a rubber spatula as needed. Add in the two egg yolks and the vanilla. Beat on medium-high speed until combined. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed.

With the mixer on low speed, slowly add in the dry ingredients and the milk, alternating little by little. Fold whipped egg whites into the cupcake batter. The batter will be smooth, velvety, and slightly thick.

Spoon batter into cupcake liners filling halfway full. Bake for 18-21 minutes or until a toothpick inserted in the center comes out clean. Allow to cool in the pan for 5 minutes, then transfer to a rack to cool completely.

While the cupcakes are cooling, make the frosting. Cream together the butter and cocoa powder. Add in the powdered sugar one cup at a time, mixing well. Add in the vanilla and salt. Finally, add in the milk or cream, one tbsp at a time, until the frosting reaches a smooth consistency. Transfer to a piping bag and pipe onto the cooled cupcakes. Add sprinkles if desired. Enjoy!