Preheat oven to 350ºF (177ºC). Line a standard cupcake pan with cupcake liners and set aside.
In a medium size bowl, whisk together flour, cornstarch, baking powder, and salt. Set aside.
In a large bowl with a handheld mixer, or the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar together on medium speed until light and fluffy, about 3 minutes. Add the egg whites, vanilla extract, and almond extract, and beat again until everything is incorporated.
Stop the mixer, scrape down the sides and bottom of the bowl, then beat in the yogurt on medium speed until completely combined.
Add the dry ingredients in 2 additions, alternating with the milk, beating on high for about 10 seconds once everything is combined. Remove bowl from mixer and stir in the sprinkles carefully with a spatula.
Fill cupcake liners ¾ of the way full (I like to use an ice cream scoop with a thumb trigger) and bake for 15-18 minutes or until a toothpick inserted in the center comes out clean. Remove from oven and allow to cool completely on a wire rack before decorating.
In a large bowl with a handheld mixer, or a stand mixer fitted with the paddle attachment, beat the butter on medium speed until creamy, about 2 minutes.
With the mixer on low, add in the powdered sugar, vanilla extract, almond extract, and milk or cream. Increase mixer speed to medium and beat until completely smooth, about 3 minutes. Add salt to taste. Stir in sprinkles carefully with a spatula. If frosting is too stiff, add more milk. If it is too thin, add more powdered sugar.
Fill a piping bag (or a large zip top bag with the corner snipped off) with frosting and decorate your cupcakes. If you want a fancier pipe, use a Wilton 1M tip. More sprinkles on top are optional. Cupcakes stay fresh in an airtight container at room temperature up to 3 days.
Room temperature eggs: these are always a good idea when using room temperature butter as it makes for easier incorporation into the batter. To bring eggs to room temperature quickly, place eggs in a bowl of warm water for 5-10 minutes.
Full fat dairy: it is imperative to use full fat dairy in this recipe for moisture, since we're eliminating the yolks from the eggs to keep the batter light.
Coloring icing: I like to color my funfetti buttercream, and my favorite coloring are AmeriColor. The color I used in the photos is "dusty rose."
This recipe can make about 2 and ½ dozen mini cupcakes (baking time is 11-13 minutes).