Vanilla Chocolate Marbled Angel Food Cake

Ingredients
* 12 large egg whites
* 1 1/2 tsp cream or tartar
* 1/4 tsp salt
* 1 1/3 cups superfine sugar
* 1 tsp vanilla
* 3/4 cup cake flour, divided
* 1/3 cup unsweetened cocoa powder

Directions
1. Heat oven to 350 F
2. Bring the egg whites to room temperature in your mixing bowl. When brought up to temperature, add the cream of tartar and salt.
3. Beat the egg mixture until frothy. Gradually beat in the sugar one tablespoon at a time over about 7 minutes. The whites should be stiff with glossy peaks. Add in the vanilla extract.
4. Put half the egg whites mixture into a separate bowl. In one bowl, fold in 1/2 cup of flour, being careful to not deflate the egg whites too much. Ensure the flour is fully incorporated.
5. In the other half, add the remaining 1/4 cup of flour. Sift the cocoa powder directly onto the mixture. Fold the flour and cocoa into the egg whites, again trying not to deflate the egg whites too much. Ensure the flour and cocoa are fully incorporated.
6. Spoon alternating batters into an un-greased tube pan. Swirl the batters together with a knife to create the marbled effect.
7. Bake at 350 F for 35 to 40 minutes. The cake should be very high and cracked and golden on top. Remove from the oven and invert to cool completely.
8. To remove, run a knife around the edge and gently let the cake fall out of the pan.

Notes
A tube pan is not a bundt pan. Also, a wine bottle works perfectly for inverting the cake to cool.