In a heavy-bottomed 4 quart pot over medium-high heat, melt butter and/or oil then whisk in flour.
Cook, stirring continuously, until roux turns the color of peanut butter, then carefully stir in the onion, celery and bell pepper, and reduce heat to medium.
Add garlic and chopped shrimp, then stir and cook until shrimp are pink.
Add thyme and sausage, then whisk in broth -- about 1/2 cup at a time. When all broth is added, bring to a boil, whisking, then reduce heat to medium low.
Add tomatoes, tomato paste, and bouquet garni and cook, stirring from time to time, for 15 minutes, until stew is thickened and the flavor starts to develop.
Season to taste with salt, pepper and condiments.
While stew is cooking, sauté the whole shrimp (peeled and deveined, but not chopped) in a little oil or butter, and add to stew just before serving.
Serve with hot rice, mixed with chopped green onions.
