if prepared a day or two in advance and refrigerated. Let the gumbo cool completely at room temperature, uncovered, before refrigerating. Reheat over medium-low heat, stirring occasionally. Just before serving, remove the gumbo from the heat. Taste for seasoning++it should be spicy. Stir in the file powder to taste. (Note: File powder turns stringy as it cooks, so it should not be added to the gumbo until the pot has been removed from the heat.) Transfer the gumbo to a heated tureen and serve it immediately, accompanied by a bowl of rice. To serve, place about 1/2 cup rice to one side of a heated soup plate.. Ladle the gumbo around the rice and garnish each serving with a sprinkle of finely chopped green onions. Serves 8.