Makes three cakes; cut each 5x8, to produce 40 pieces per cake.
If you use only 1/6 of the amount of ingredients listed, you will have enough cake batter and frosting for a 9x13" sheet cake, OR two 9-inch cake layers (you'll need about 1/5 of the amount of frosting in order to have enough for a layer cake). Bake for slightly less time for a smaller cake.
Adapted from recipes by Smittenkitchen.com and Cooks Illustrated
All ingredients should be room temperature.
24 ¾ cups (6 lbs 3 oz) cake flour
4 T. baking powder
3 T baking soda
2 T salt
3 lbs (12 sticks) butter, softened
12 cups (2400g) sugar
4 T vanilla extract
24 large eggs
12 cups buttermilk
Preheat oven to 350f “speed bake”. Grease and flour 3 full size long pans (hotel pans).
Sift flour, baking powder, baking soda, and salt into a large bowl.
In an even larger bowl, beat butter and sugar together till pale and fluffy; add vanilla.
Add eggs 4 at a time, mixing and scraping each time.
On low, beat in buttermilk till just combined (mixture will look curdled).
Add flour mixture into liquid in three batches, mixing just till incorporated.
Pour evenly into prepared pans. Rap each pan sharply on the counter a few times, to eliminate large bubbles in the batter, then bake till golden brown (pick should come out clean), 35-50 minutes. If you peek in the oven window after fifteen minutes and the edges are browning too quickly, you can turn the heat down to 325f for the next fifteen minutes or so.
Dark Chocolate Frosting
12.5 sticks butter, softened to 60-65f
5 cups (20 oz) confectioners sugar
3 ¾ cups dutch cocoa
¼ tsp. Salt
3 ¾ cups light corn syrup
5 tsp. Vanilla
2.5 lbs bittersweet chocolate, melted and cooled 85f-100f
Note: If you have a small food processor, prepare the frosting in three batches, using 1/3 of the ingredients each time.
Process butter, sugar, cocoa and salt until smooth, about 30 seconds.
Add corn syrup and vanilla, and process till just combined. Then add chocolate and pulse till smooth and creamy.
The frosting can be held for three hours; for longer storage, refrigerate and allow to come to room temperature for one hour before using.