Heat stock in a medium saucepan; cover and keep warm over low heat. In a 4- to 5-quart Dutch oven or heavy-bottomed soup pot, heat oil over medium-high heat. Whisk in flour and continue to whisk constantly, scraping sides and bottom to prevent burning. Continue until mixture (known as a roux) becomes silky and a light milk chocolate color, about 5 minutes. Be careful not to let it scorch.Advertisement
As soon as the color is right, reduce heat to medium-low. Add onion, bell pepper and celery; cook, stirring occasionally, until vegetables are just softened, 3 to 4 minutes. (The roux will continue to darken slightly to a dark milk chocolate color.) Remove from heat and transfer to a bowl. Measure 1 1/2 cups and return that amount to Dutch oven.
Return heat to medium-low. Add mushrooms (if using), carrot and minced garlic; cook, stirring occasionally, until carrot is tender but not soft, 3 to 4 minutes. Whisk in 4 cups warm stock, the tomatoes, soy sauce, Cajun seasoning, thyme, garlic powder, onion powder and cayenne pepper. Bring to a boil, stirring frequently. If soup seems too thin, add more roux, 1/4 cup at a time, until soup reaches desired thickness. Reduce heat and simmer, uncovered, 45 minutes to develop flavor, adding broth or roux to thin or thicken soup if desired.
Add corn, peas and okra; return to a boil. Reduce heat to low and simmer until vegetables are tender, 5 to 10 minutes. Season to taste with salt and black pepper. Serve over brown rice, topped with a sprinkle of gumbo filé powder, if desired.
What's gumbo file powder?
Made from dried sassafras leaves, this traditional seasoning has a woodsy flavor similar to root beer. It’s added as an accent right before serving. Find it in specialty stores or online, but don’t sweat it too much if you can’t find it.