1. Heat 1 tablespoon oil in a large soup pot over medium-high heat. Add sausage, and cook 3 to 4 minutes or until browned on all sides. Transfer sausage to a plate with a slotted spoon.
2. Add remaining oil to drippings in pot to equal 1⁄4 cup. Whisk in flour. Cook over low heat, stirring frequently, 20 minutes or until mixture is dark reddish-brown.
3. Stir in onion and next 4 ingredients, and sauté over medium heat 8 minutes or until softened. Stir in stock and next 8 ingredients. Bring to a boil, reduce heat, and simmer, covered, 30 minutes.
4. Meanwhile, cook grits according to package directions. Cover, and keep warm.
5. Stir in sausage and shrimp, and cook 4 minutes or until shrimp are done. Add crab, and simmer until heated. Remove bay leaves, and stir in parsley and, if desired, filé powder. Serve gumbo over grits. Season with hot sauce, if desired.