Chop 2 medium onions and saute in 3 tablespoons butter. Just until soft but not brown. Add 4 tablespoons flour. Stir to blend. Add one quart chicken broth. Slice and brown 1 lb. mushrooms. Add liquid from mushrooms to broth. Simmer 5 minutes, until thickened. Add 1 pint light cream and the mushrooms. Heat to simmer (do not boil). Season with salt, white pepper and mace.