Fry an onion, chopped fine, in an ounce of butter until it is a golden color, adding a tablespoonful of flour to make a roux. Moisten with half a pint of stock, stirring well and often until the sauce hardens. Season with half a tablespoonful of salt, a little white pepper, the same of cayenne, a tablespoonful of Worcestershire sauce, half a teaspoonful of mustard, a crushed grain of garlic, and a teaspoonful of chopped parsley. Stir this well, adding two pounds of cooked lobster cut in small pieces, with twelve mushrooms, also chopped up very small. Cook for thirty minutes in a saucepan, then put it back off the hot fire; add the yolks of four eggs, stir again for a moment, cool, and use as required.