Preheat your oven to 350°F and line a muffin pan with cupcake liners. If using a 12-hole muffin pan, you will need to use 2 for the 16 cupcakes.
Beat the egg whites with a mixer until fluffy and soft peaks form, about 2-3 minutes. Set aside.
Mix the flour, baking powder, and salt in a medium bowl and set aside.
In a separate bowl, cream the softened butter and sugar together until smooth, then add the egg yolks and vanilla, mixing until well combined.
Gradually mix the dry ingredients and milk into the creamed butter mixture, alternating between them, starting and ending with the dry ingredients.
Gently fold the whipped egg whites into the batter.
Fill the cupcake liners halfway with the batter and bake for 18-20 minutes.
Once baked, let the cupcakes cool in the baking pan for 1 hour before topping with milk chocolate frosting and adding sprinkles.