Step 1Peel and devein the shrimp, reserving the shells. Set the shrimp aside. Rinse the reserved shrimp shells under cold running water and place in a saucepan filled with 4 cups water. Bring to a boil, reduce the heat and simmer for 15 minutes. Strain, reserving the stock and discarding the shells.
Step 2Make the roux by melting the butter in a large skillet over low heat. Whisk in the flour and cook, stirring constantly, until the roux is a caramel brown color, about 25 to 30 minutes. If it burns even slightly, throw it out and start over.
Step 3Remove the roux from the heat. Mix together the gumbo file and one-half cup hot water until smooth. Spoon the roux, 3 1/2 cups water and the file mixture into a large stockpot over low heat. Stir in the onion, green onion, celery, one-third cup Bayou Magic, garlic, 1 tablespoon Old Bay, parsley, smoked turkey ham, chicken stock and shrimp stock. Stir occasionally.
Step 4Simmer, covered, on very low heat for 3 hours, stirring occasionally.
Step 5About 1 hour before the gumbo is done, heat the vegetable oil in a large skillet and add the chicken. Cook for 8 to 10 minutes over medium-high heat to brown on all sides. Remove to a bowl and add the sliced sausage to the skillet, in batches if necessary. Cook until slightly brown; remove to a bowl. Add the chicken and sausage to the gumbo during the last hour of cooking.
Step 6Add 1 tablespoon Bayou Magic to a medium saucepan of boiling water. Add the shelled shrimp. Remove from the heat and let the shrimp sit in the seasoned water for 30 minutes.
Step 7Heat the crab in a small pot of boiling water with one-half tablespoon of Old Bay. The crab is already cooked; you're just adding flavor and heating it before you serve. Remove the crab from the spiced liquid with a slotted spoon.
Step 8To serve, spoon rice (if using) into bowls, then ladle a cup of gumbo into each bowl and place about 5 shrimp and several tablespoons of crab on top.