I think I might actually get a stomach ache from all the cakes I've been tasting and re-tasting (for science!) with The Great High Altitude Baking Experiment of '16, but I'm finally there! I finally have a white cake that works! It's stable! The top is perfectly level! No sunken centers! It only took three attempts this time, and the winner recipe is Rose Levy Beranbaum's white velvet cake. I couldn't be bothered to take a picture, because cake #7, but it's most definitely level, with a smooth (dare I say, velvety?) crumb. Taste- and texture-wise, it was my favorite of the three tried. Here are my adaptations for high altitude:
White Velvet Cake
Makes 2, 8" cake layers
Ingredients (everything room temp.):
188 g. egg whites
280 g. (~10oz) whole milk, divided
2 1/2 teaspoons vanilla
360 g. cake flour
350 g. sugar
4 teaspoons baking powder
3/4 teaspoon salt
1 stick + 6 tablespoons (200 g) unsalted butter
Preheat oven to 360 degrees. Grease and line with parchment two 8-inch round cake pans.
In a small bowl, combine 1/4 cup milk with eggs and vanilla.
In the bowl of a stand mixer, combine all dry ingredients and mix on low for a few seconds. Add softened butter and remaining milk and mix on medium for 1 1/2 minutes. Add egg mixture in 3 parts, starting on low speed then turning it up to medium and beating for 20 seconds after each addition.
Scrape batter between prepared pans and bake in center of oven for 35-45 minutes (mine need 43 minutes). Let cool 10 minutes before turning out onto cooling racks.