Crawfish Étouffée

1 pound crawfish tails, with fat
8 tablespoons (1 stick) butter
1 medium - large onion, chopped
5 cloves garlic
2 tablespoons bell pepper, minced
1/2 stalk celery, minced
Green onion tops
Fresh parsley
2 teaspoons tomato paste
Cayenne pepper
Freshly ground black pepper
Salt
2 tablespoons flour
1 - 2 cups water (or substitute broth or beer)

Melt butter in pot, add flour and stir constantly. Cook roux until a nice deep brown is achieved, but be careful not to burn it. Add onions, bell pepper, celery and garlic. Cook until tender, and keep stirring. Add crawfish fat, if possible, and cook down 10-15 minutes. Add tails and tomato paste, then add water. Cook down for 20 minutes or so, but be careful not to overdo it. Add salt and peppers to taste. Cook a little more, then add chopped green onion tops and parsley and cook till ready. Serve over rice.