In a large sauté pan, melt the butter over medium-high heat. When the foam has subsided and the butter is just beginning to turn brown, add the white mushrooms and sauté, stirring, for 1 minute; then add the shiitakes and stir for another minute; finally, add the oysters and chanterelles, if using. Cook the mushrooms until all their liquid has evaporated, about 5 to 6 minut