INGREDIENTS
1 tbsp
Orange, zest
3
Egg whites
1 3/4 cups
All-purpose flour
1/2 tsp
Baking powder
1/4 tsp
Baking soda
4 cups
Confectioners sugar
1 cup
Granulated sugar
1 pinch
Salt
1 1/4 tsp
Vanilla
2 1/3 tbsp
Orange juice, freshly-squeezed
1 1/2 cups
Butter, unsalted
1/3 cup
Sour cream
1 1/4 cups
Champagne