• Preheat the oven to 350 degrees F. Grease and flour two 6-inch round metal cake pans.
• Sift your cake flour and weigh it to make sure you are using 114 grams, then sift together the flour and baking powder. Add the salt and stir until thoroughly blended.
• Beat the egg whites until stiff peaks form and set aside.
• In a mixing bowl, using an electric mixer, beat the butter until creamy. Add the sugar and continue to beat for about 3 minutes, scraping the bowl often. Add the egg yolks, one at a time, beating until blended, then beat in the vanilla.
• Fold the flour mixture into the butter mixture alternately with the sour cream, scraping bowl often. When everything is thoroughly blended, beat with the electric mixer for 30-40 seconds, scraping bowl.
• Using a heavy duty scraper, fold in the beaten egg whites.
• Scrape the batter into the prepared pans (about 10 oz per pan) and smooth evenly.
• Bake at 350 for about 30 minutes or until cakes spring back when touched. Let cool for 10 minutes, then carefully turn from pans onto a rack. Make the frosting.

Chocolate Frosting

• Note: Be sure to measure your confectioners' sugar carefully. I recommend taking the time to sift it for frosting. Also, sift the cocoa if it is lumpy.
• Make sure all your ingredients are at room temperature. The butter should not be too cold, nor should it be melted.
• In a large mixing bowl or the bowl of a stand mixer, mix the butter, sour cream, sugar, cocoa, salt and 2 tablespoons of the milk until it all starts to come together as a thick sludge.
• When everything is sticking together, add the vanilla. Increase mixer speed and beat until smooth, scraping bowl and adding more half and half (or milk and cream) as needed until you get your desired texture consistency. Spread over the cake.