Vanilla Bean Birthday Cake

Directions

1. 1
   Stir the milk, egg whites, vanilla extract and vanilla bean seeds in a large bowl until combined. Set aside.
2. 2
   In a separate bowl of a KitchenAid(R) Stand Mixer with the flat beater attachment, stir the cake flour, sugar, baking powder and salt until combined. Add the butter, in cubes, and stir until the mixture resembles coarse crumbs - almost like you would for pie or biscuit dough.
3. 3
   Beat in the milk mixture for a few minutes so everything is well combined and you get a bit of air into the batter so the cake becomes light and fluffy.
4. 4
   Pour the batter into your prepared cake pans and bake on the center rack of the oven until a toothpick inserted in the center comes out clean (30 minutes for 8-inch pans, maybe a little less time for 9-inch pans). Let the cakes cool in the pans for five minutes, then carefully invert the pans and remove the cakes. Transfer the cakes to a cooling rack to cool completely. Once cooled, use a serrated knife to slice the domed tops off the cakes so they are flat on both sides. This allows the cake to be evenly layered and frosted well.
5. 5
   Heat oven to 350°F. Spray two KitchenAid(R) Professional-Grade Nonstick 8x2 Round Pans with baking spray. Line cake pan bottoms with parchment paper, then spray paper. Dust pans with flour; invert and rap pans to remove excess flour.
6. 6
   In a large bowl, stir milk, egg whites, vanilla and vanilla bean seeds until combined.
7. 7
   In a bowl of a KitchenAid(R) Classic Series 4.5-Quart Tilt-Head Stand Mixer with a flat beater attachment, stir cake flour, sugar, baking powder and salt until combined. Cut butter into cubes and add to bowl; stir on low speed 2 minutes until mixture resembles coarse crumbs.
8. 8
   Add milk mixture to flour mixture and beat on medium speed 2 minutes. Scrape sides of bowl and beat another 15 seconds.
9. 9
   Divide batter between prepared cake pans. Bake on center rack 30 to 35 minutes until a toothpick or cake tester comes out clean. Cool cakes in pans 5 minutes, then carefully invert cakes and transfer, flat-side down, to a cooling rack to cool completely, 1 to 1 1/2 hours.
10. 10
    Meanwhile, make the frosting: In a clean bowl of a KitchenAid(R) Stand Mixer with the flat beater attachment, beat butter on medium speed 3 minutes until soft, light and fluffy. Add 3 1/2 cups powdered sugar, 1/2 cup at a time, beating on high speed after each addition until just combined.
11. 11
    Add 2 tablespoons milk, plus vanilla and salt. Stir until combined.
12. 12
    Frosting should be a firm, yet smooth and spreadable consistency. If too soft, stir in remaining 1/2 cup powdered sugar 1 tablespoon at a time until firm. If too firm, stir in more milk 1 tablespoon at a time until soft.
13. 13
    Use a serrated knife to trim domed tops of fully cooled cakes to create a flat surface. Place one cake, cut-side up, on a cake stand or serving plate. Use an offset spatula to frost top of cake. Top with second cake, cut-side down. Frost sides and top of cakes. Decorate with nonpareil sprinkles, if desired.