Red Seal Cook

Answer: B - Steam is the key leavener in any recipe that uses pâte à choux, such as profiteroles. While the eggs in the recipe do slightly contribute to leavening, the main source of both the leavening and signature hollow center of the finished product is caused by steam. Traditionally, no chemical leavening agents, such as baking powder, are required for pâte à choux. However, in large-scale operations, baking ammonia can be incorporated into the recipe in order to ensure sufficient rise and a crisp exterior surface.