Here's what you need:
2 1/4 cups cake flour (I used Swan’s Down brand)
1 tablespoon baking powder
1/2 teaspoon kosher salt
1 1/4 cups whole milk, room temperature
4 large egg whites, room temperature
1 stick (8 tablespoons) unsalted butter, at room temperature
1 1/2 cups sugar
seeds scraped from one vanilla bean (or 1 tsp vanilla bean paste)
2 teaspoons pure vanilla extract
1/3 C sprinkles or jimmies**
** I know you can use regular old non pareil sprinkles but I found that the softer confetti dot sprinkles- ( I believe they are made from fondant) like these from Etsy work really well and give you more color since they are larger . .. and i just like the colors too!
Center a rack in the oven to 350 degrees F. Line cupcake pan with paper liners.
In a large bowl, sift together the flour, baking powder and salt, set aside. In a medium bowl, whisk together the milk and egg whites. Then in the bowl of a stand mixer fitted with the paddle attachment beat the butter, sugar and vanilla bean seeds (or paste) at medium speed for 3 minutes, or until the butter and sugar are very light I'd say this took about 5 minutes. Add in the vanilla extract and one third of the flour mixture, still beating on medium speed. Beat in half of the milk-egg mixture, then beat in half of the remaining dry ingredients until well incorporated. Add the rest of the milk and eggs, beating until the batter fully incorporated and smooth, then add the last of the dry ingredients.
Once ingredients are thoroughly incorporated, give the batter a good 2-minute beating to ensure that it is thoroughly mixed and well aerated. Then dump in all of your sprinkles and give it a good mix. They should be pretty well dispersed.
Using a large scoop (about 3 tablespoons), distribute the batter between 18 muffin wells, filling each well 2/3 full.
Bake for 18-24 minutes, or until a toothpick inserted into the centers come out clean. Cool on wire rack. See all those fun specks! The ones inside completely melt and just leave the fun colors!