Put the chorizo in the base of a heavy-based pot or flameproof casserole dish over a medium heat. Fry, stirring frequently, until it has rendered some fat and is crisp at the edges. Drain on paper towel and set aside.
Add the oil to the sausage fat remaining in the pot. Reduce the heat to low and sprinkle in the flour, stirring constantly, until well blended. Cook very gently, stirring occasionally, for 5 minutes until the mixture turns a rich brown.
Increase the heat slightly, stir in the celery, onions, green peppers and garlic and continue frying, stirring frequently, for 5 minutes or until soft. Add the tomatoes with their juice, the stock, okra, parsley, thyme, bay leaf and cayenne pepper. Bring to a boil, then reduce the heat, half cover the pot and simmer for 30 minutes, stirring frequently, until the okra thickens the soup. While the soup is simmering, cut the chicken into bite-sized pieces.
Increase the heat and bring the liquid to a boil. Stir in the rice, then reduce the heat to low, add the chicken and simmer for 15 to 20 minutes until the rice is tender and the chicken is cooked through. Pour in a little extra stock if needed. Add the shrimp and reserved chorizo and simmer for 1 minute or until the shrimp turn pink and the sausage is heated through.
Remove the bay leaf. Season to taste, then ladle into bowls and garnish with the reserved celery leaves. Serve with Tabasco, if you like.
Nutritional Info (Per Serving): 43 g protein, 22.5 g fat of which 5.5 g saturates, 61 g carbohydrate, 7 g fibre, 633 Calories