Cook 1 chopped shallot in a large skillet with butter until soft. Add two 10-ounce boxes frozen spinach (thawed and squeezed dry); warm through. Stir in 1 tablespoon flour, 2 teaspoons Worcestershire sauce, 1 cup chicken broth, 1/2 cup sour cream, and salt and cayenne pepper to taste. Cook 5 minutes. Add a pinch of nutmeg.