In another large skillet, melt the remaining 2 tablespoons of butter. Add the shiitake, chanterelle and oyster mushrooms, season with salt and pepper and cook over moderately high heat, stirring, until lightly browned, about 5 minutes. Add 1/4 cup of the chicken stock, cover and cook over low heat, stirring occasionally, until the mushrooms are tender, about 8 minutes. Add the remaining 1/4 cup each of cream and stock and simmer until slightly reduced, about 2 minutes. Add the creamed morels and the thyme and simmer for 3 minutes. Season with salt and pepper.