Place the flour in a large non-stick skillet and heat over medium-high heat.
Watch the pan carefully, stirring and shaking the flour. It will take about 10 to 15 minutes and the flour will turn an almond brown. Adjust the heat so that the flour does not cook too fast or burn. Remove to a plate and allow to cool.
Place the olive oil in the pan over medium heat, and add the diced onion.
Cook for about 3 minutes. Stir frequently.
Add the garlic and celery. Cook for about 2 minutes. Stir frequently.
Add the green and red peppers and cook for about 2 minutes.
Sprinkle about 1/4 of the cooked flour over the top of the cooked vegetables.
Stir to blend the flour and repeat with the flour in three more batches until it is fully incorporated and there are no clumps of flour.
Add the vegetable stock and water slowly stirring continuously.
As the sauce begins to thicken add the salt, pepper, cayenne pepper, bay leaf and Cajun spice.
Cook over medium low heat adding water a tablespoon at a time if the sauce is too thick.
Add the tomatoes, sherry, parsley and thyme. The sauce can be made to this point and kept warm or overnight.
When ready to serve heat the sauce and add the shrimp. Cook for about 8 to 10 minutes until they are pink and firm.
Serve over Brown Rice and top with the chopped green onions.
Note that the Nutrition Facts are for the Etouffee without the rice.
