5 large egg whites at room temperature
1/2 cup sour cream at room temperature
1 cup buttermilk at room temperature
3 tsp clear vanilla extract
3 cups plus 3 TBS cake flour
1-3/4 cup sugar
1 TBS baking powder
3/4 tsp salt
1 cup unsalted butter at room temperature and cut into cubes
For the buttercream
2 cups unsalted butter, slightly chilled
6 cups powdered sugar measured then sifted
3-4 TBS heavy whipping cream
2 tsp clear vanilla extract
pinch of salt
This is enough frosting to fill and cover cake
1. Preheat oven to 325℉. Spray three 8-inch round baking pans with nonstick spray (or four 6 inch), line the bottom of each pan with parchment paper and spray again. Set aside. (or line or spray muffin pans for cupcakes I got 30)
2. In a medium bowl or measuring cup, combine and stir the egg whites, and vanilla. Set aside.
3. In the bowl of an electric mixer, combine the butter and sugar. Beat until light and fluffy, about 2 minutes on medium speed.
4. Add the egg mixture, followed by the sour cream. Mix until combined (it will appear a little curdled it's fine)
5. In a separate bowl, whisk together the flour, the baking powder and the salt.
6. With the mixer on low, alternately add the flour mixture and the buttermilk, starting and ending with the flour.
7. Divide batter evenly among your pans. (Use a kitchen scale 12 oz of batter in 6-inch pans, 16 oz of batter in 8-inch pans) Spread evenly with a small offset pallet knife. Or if making cupcakes evenly distribute in liners)
8. Bake until a toothpick comes out with a few crumbs when inserted into the center, about 23 to 28 minutes. Check at 23 minutes and set timer foe 2-3 minute interval if the cake needs to be baked longer. (My cupcakes took about 20 minutes).
9. Let the cake layers cool on racks for 10 minutes before inverting onto greased wire racks. Gently turn the cakes back up so the tops are up and cool completely. Once the cakes are cooled completely, level the tops if needed.
10. Wrap each cake layer with plastic wrap and chill in the freezer for at least an hour before using. The cake layers can be stored for up to a few days wrapped once in plastic wrap and frozen. To store longer than a few days, wrap twice in plastic wrap, then in foil, and seal in a ziplock bag.
FOR THE BUTTERCREAM
1. In the bowl of a stand mixer fitted with a paddle attachments, cream the butter for about 2 minutes. This will soften the butter without it having to be warm.
2. With the mixer on low speed, gradually add the sifted powdered sugar, one cup at a time, mixing a little in between each addition.
3. With mixer on medium speed, add whipping cream, vanilla and salt.
4. Turn the mixer to medium-high speed and beat for an additional 5 to 7 minutes. The frosting will become lighter in color and texture.
5. Before spreading on the cake, spend a couple minutes mixing the buttercream by hand with a wooden spoon to push out the air pockets.
To Assemble
1. Place the first cake layer, top side up. For the 6-inch cake, add about 1/2 cup frosting on the lake layer. For the 8 inch version, add about 1 cup frosting. Spread over the cake layers as evenly as possible. Make sure to get eye level with the cake to ensure the frosting is spread evenly over the cake.
2. Repeat this step until you get to the final cake layer, which you will lay top side down.
3. Apply a thin coat of frosting around the entire cake to lock in the crumbs. Freeze for about 10 minutes. After the crumb coat is set, continue frosting and decorating the cake.
from Cake by Courtney
For the cupcakes I used Raspberry buttercream
1 cup butter
5 cups powdered sugar
6 oz raspberries, mashed and then deseeded through a sieve.
1. Mix butter and raspberry together. Add powdered sugar and beat until well combined.