Sauté the onion for a couple minutes, adding a bit of water if it sticks.
Add the garlic, and cook another minute.
Add the wine and let it cook away.
Add the tomato paste, herbs, and mushrooms. Sauté a few minutes, then add the vegetable broth and soy sauce.
Cook over low heat for 2-3 minutes. Dissolve the cornstarch in two tablespoons of water and whisk it into the stew. Stir and cook 2-3 minutes until the stew thickens.
Dish out a cup of polenta into an individual plate, and spoon the mushroom stew over it. Sprinkle with chopped parsley.