Chocolate Brownie Cake

I'm making this for our church picnic this Sunday. I am having Bodie this weekend, so I will make it and freeze it until Sunday morning. I won't frost it until Sunday, but I am going to go ahead and make the frosting today and keep it in the refrigerator. FoodNetwork's Emeril Lagasse
Ingredients:
1/2 pound btter, softened at room temperature
2 cups sugar
2 eggs
2 cups all-purpose flour
1 teaspoon baking soda
4 Tablespoons cocoa powder
1/2 cup butermilk
/2 cup sour cream
1 teaspoon vanilla extract
Chocolate Buttermilk Frosting, recipe follows
Preheat oven to 350 degrees Grease and flour 2 (9inch) cake pans, then line with parchment paper.
In the bowl of an electric mixer, cream butter and sugar until light and fluffy. Add the eggs and mix until thoroughly combined.
In a medium mixing bowl combine sifted flour, baking soda, and cocoa powder together.
In a small mixing bowl whisk the buttermilk, sour cream and vanilla together.
While the mixer with the butter mixture is on low speed, add the dry ingredients in 3 batches, alternating with the liquid ingredients.  Divide the cake batter evenly among the 2 prepared cake pans and bake until a toothpick inserted in the middle of the cake, comes out clean and the edges of the cake just begin to pull away from the sides of the pan, about 30-35 min. Transfer the cakes to a cooling rack and allow the cakes to cool in the pans. Carefully remove the cakes from the pans and frost as usual for a layered cake with the Chocolate Buttermilk Frosting.
Chocolate Buttermilk Frosting
1 stick butter, softened
1/4 cup cocoa powder, sifted
8 ounces cream cheese
1 pound powdered sugar, sifted
2 Tablespoons buttermilk
1 teaspoon vanilla
In the bowl of the electric mixer combine the butter, cocoa powder and cream cheese over low speed and mix until thoroughly combined. Increase speed to high and cream ingredients until light and fluffy. Reduce speed to low and slowly add the powdered sugar, buttermilk, and vanilla. Beat until mixture is smooth and thoroughly combined.