Place mushroom stems in a pot with 4 cups water. Bring to a boil, reduce heat, and simmer for 25 to 30 minutes. Remove stems and reduce liquid by half. You now have about 2 cups of mushroom stock.
Sauté portobello mushrooms in oil for 4 to 5 minutes. Using a slotted spoon, transfer mushrooms to a bowl. Add celery and onion to oil and wilt down for 4 to 5 minutes. Add garlic and cook for 1 minute. Then add flour to make a light roux. Add mushroom stock, vegetable stock, and red wine if desired; stir well to eliminate lumps. Add sautéed mushrooms, shiitake mushrooms, domestic mushrooms, tomatoes, tomato paste, roasted red bell pepper, cayenne, and thyme; stir to mix. Simmer over medium heat for 35 to 40 minutes.  Correct seasoning with salt and pepper.

Meanwhile, sautee spinach  in 1 tablespoon vegetable oil until withered; drain if necessary. Season with salt and pepper.

To serve, spoon grits or rice onto individual serving plates, top with sauteed spinach, spoon grillades atop spinach. Garnish with green onions.