Melt the butter in large skillet. Add onions and shallots and cook briefly over medium high heat. Add mushrooms and continue to saute, stirring frequently until all of the liquid that is released from the mushrooms has evaporated, about 20 minutes. Once the mushrooms are darkened and dry, add the salt, pepper, and Madeira. Continue to cook until the liquid has evaporated and the mixture is thick again, about five or six minutes more. Adjust the seasonings.

a bowl and surround with Melba Toast or other fine cracker.

Duxelles will keep refrigerated up to two weeks or frozen for three months. Before using, reheat in micro to soften.