1. Heat the oil in a large heavy pot or Dutch oven over medium high heat. Add the andouille and cook until brown and crisp, turning occasionally, 7 minutes. Remove with a slotted spoon to a plate. Add the Cajun seasoning, celery, onions and bell peppers and stir. Reduce the heat to medium and cook until the vegetables are very soft, 10 minutes. Stir in the tomatoes, Worcestershire sauce, hot sauce and the scallion whites and cook until thickened, 3 minutes. Stir in the andouille, chicken stock and rice. Bring to a simmer, reduce the heat to medium low, cover and cook until the rice is tender, 15 to 20 minutes.
2. While the rice cooks, prepare the shrimp. Lightly sprinkle the shrimp with Cajun seasoning. Heat some vegetable oil in a medium nonstick skillet over high heat. Add the shrimp and cook in batches if necessary, turning once, until the shrimp are crisp and cooked through and the tails are bright pink, 5 minutes per batch.
3. Stir half of the scallion greens into the rice. Divide into bowls, top with the shrimp and garnish with the remaining scallion greens.
NotesCook's Note: If you can't find a 14.5-ounce can of tomatoes, use half of a large can and save the remaining tomatoes in the refrigerator up to a week for another use.