2 1/2 cups milk , warmed to lukewarm
1 cup flour
1/2 cup cocoa powder
4 eggs, separated
1/8 teaspoon distilled vinegar
1 3/4 cups powdered sugar
3 tbsp Cointreau
1/2 tsp vanilla extract
Based on a recipe from here
Combine the flour and cocoa powder.
Whip the egg whites with vinegar until stiff peaks form and set aside.
Beat the egg yolks and sugar until light in color. Beat in the melted butter, Cointreau, and vanilla extract for about 2 minutes.
Add in the combined flour and cocoa alternately with the milk into the batter.
Fold in the egg whites, 1/3 at a time. The batter will be somewhat lumpy.
Pour the batter into the greased pan and bake for 50-60 minutes. The cake should have a slight jiggle when done.
Garnish with confectioner’s sugar and orange slices.