In a very large, deep skillet, heat the 3 tablespoons of olive oil. Add the shallots and cook over moderate heat until fragrant, about 1 minute. Add the shiitake, season with salt and pepper and cook, stirring once or twice, until the mushrooms are golden and tender, about 8 minutes. Add the cream and bring to a boil. Simmer until slightly reduced, about 4 minutes.