1Cook the white rice according to package directions and keep warm.
2Heat the vegetable oil in the dutch oven over medium heat. Whisk in the flour and stir constantly with a wooden spoon for 20 to 25 minutes until the roux turns the color of peanut butter. Lower the heat if it darkens too fast.
3Add the onion, bell pepper, celery, and the white parts of the green onion to the roux. Cook 6 to 8 minutes, stirring often, until soft.
4Stir in the garlic and cook 1 minute more until fragrant.
5Add the andouille and cook 4 minutes until lightly browned at the edges.
6Pour in the chicken broth, then add the diced tomatoes, bay leaves, thyme, smoked paprika, and cayenne. Stir well to lift the browned bits from the bottom.
7Simmer the broth uncovered over medium-low heat for 25 minutes, skimming any foam from the surface.
8While the gumbo simmers, place the shrimp shells in a small saucepan with 2 cups water and simmer 15 minutes. Strain and add the liquid to the gumbo for extra shellfish flavor.
9Season the gumbo with hot sauce, salt, and pepper. Add the shrimp and cook 3 to 4 minutes, just until pink and opaque.
10Remove the bay leaves. Stir in the green onion greens and most of the parsley. Serve over rice, topped with the remaining parsley.