In medium skillet over medium heat, melt remaining 1 tablespoon butter. Add onion and cook until soft. Reduce heat to medium-low. In medium bowl, whisk eggs, yolks and all but 1 tablespoon heavy cream. Stir in pepper and nutmeg. Add 1 cup Gruyere and transfer to skillet. Stir until eggs just begin to set. Transfer to bowl and stir to cool. Add bacon and set aside.