Make the Dark Roux: This is the most crucial step and requires your full attention. In a large, heavy-bottomed pot or Dutch oven, combine the flour and oil (or butter). Turn the heat to medium-low. Cook, stirring constantly and slowly with a flat-edged wooden spoon or heatproof spatula, for 30-45 minutes. Scrape the bottom of the pot continuously to prevent scorching. The mixture will go through several stages: from a pale paste to a blonde color, then to a peanut butter color, a copper penny color, and finally, a deep milk chocolate brown. The aroma will become nutty and toasted. Once you reach your desired dark brown color, immediately proceed to the next step. If you see black specks or it smells burnt, you must discard it and start over. There is no saving a burnt roux.

Sauté the Trinity: Immediately add the diced onion, bell pepper, and celery (the “Holy Trinity”) to the hot roux. Stir vigorously. The cool vegetables will stop the roux from cooking further and will sizzle and steam. Continue to cook, stirring frequently, for about 7-10 minutes, until the vegetables have softened.

Cook the Mushrooms and Garlic: In a separate large skillet, heat the 2 tablespoons of olive oil over medium-high heat. Add the sliced mushrooms in a single layer (you may need to do this in two batches). Cook without moving for 3-4 minutes, until the bottoms are deeply browned. Stir and continue to cook until the mushrooms have released their liquid and are browned all over. Add the browned mushrooms to the pot with the trinity. Add the minced garlic to the pot and cook for 1 minute more, until fragrant.

Build the Gumbo: Slowly pour the warmed vegetable broth into the pot, about one cup at a time, whisking constantly to ensure the roux dissolves smoothly into the liquid without lumps. Once all the broth is incorporated, stir in the undrained diced tomatoes, bay leaves, smoked paprika, thyme, oregano, cayenne pepper, and vegan Worcestershire sauce.

Simmer for Flavor: Bring the gumbo to a gentle boil, then reduce the heat to low. Let it simmer, partially covered, for at least 1 hour, stirring occasionally. This long simmer is essential for the flavors to meld and deepen. The gumbo should thicken slightly and develop a rich, dark color.

Add the Okra and Beans: After the initial simmer, stir in the frozen okra and the rinsed kidney beans (if using). Increase the heat to medium-low and continue to cook for another 20-30 minutes, or until the okra is tender. The okra will also act as a natural thickener.

Finish and Season: Remove the pot from the heat and discard the bay leaves. Stir in the fresh parsley and most of the sliced green onions, reserving some for garnish. Taste the gumbo carefully. At this point, season it generously with salt and freshly ground black pepper until the flavors are bold and balanced.