Preheat oven to 350 degrees. Line 24 cupcake pans with paper liners.
Combine egg whites, milk, almond extract and vanilla paste in a large liquid measuring cup. Mix with a fork until blended.
Mix cake flour, sugar, baking powder, and salt in bowl of a stand mixer. Add butter and beat on low speed until mixture resembles moist crumbs, with no powdery streaks remaining.
Add all but 1/2 cup of milk mixture and beat at medium speed for 1½ minutes. Add remaining ½ cup of milk mixture and beat 30 seconds more. Stop mixer and scrape sides of bowl. Return mixer to medium (or high) speed and beat 30 seconds longer.
Divide batter evenly between cupcake cups . Bake on center rack for 20 minutes or until cupcakes test done – a toothpick should come out with moist crumbs.
Let cupcakes rest in the pan for about 5 minutes, then carefully remove them from the pans and let them cool on a rack.
To make icing, mix together the butter and powdered sugar. Mix in the vanilla bean paste and some of the milk. Beat on high until light and creamy, scraping sides of bowl. Add remaining milk if needed. Taste test and add more sugar, vanilla bean paste or milk to get the consistency you want.
Makes 24 cupcakes