Shrimp Etouffe'e

8 Tbsp. (1 stick) unsalted butter
2 cups onions, chopped
1 cup celery, chopped
1 cup bell peppers, chopped
1 tsp. garlic, minced
1 Tbsp. tomato paste
1/2 cup green onions (tops only), chopped
1/2 cup fresh parsley, chopped
1-1/2 tsp. salt
1 tsp. cayenne pepper
3/4 tsp. black pepper
2 cups shrimp stock, recipe follows
2 lb. large shrimp, peeled
3 cups cooked wild (or white) rice

Make a stock with the shrimp shells, 2 sticks of celery, 1 medium chopped onion, 1 tsp. chopped garlic, 1 tsp. salt, and 2 quarts water. Bring to a boil, reduce heat and simmer for up to 4 hours. Drain the stock and discard all but the liquid (can be prepared ahead of time). Melt the butter in a large stockpot over high heat. Add the onions, celery, bell peppers, and garlic and saute until onions are translucent, about 6 minutes, stirring occasionally. Add the tomato paste, stirring until well blended. Add the green onions, parsley, salt, cayenne and black peppers, stirring well. Cook about 5 minutes longer scraping the bottom occasionally. Stir in the shrimp stock and bring to a boil, stirring occasionally. Reduce heat and simmer covered for 25 minutes, stirring occasionally. Add the shrimp and cook until shrimp are pink. Do not overcook. Serve immediately in bowls over rice.