For the Polenta:

1. Bring the water and salt to a boil in a medium-sized pot. Whisk gently while adding the cornmeal in a steady stream. Turn the heat to medium and continue stirring until the cornmeal has thickened substantially, about 5-7 minutes. You should be able to scrape it away from the bottom of the pan for a second before it falls back together.
2. Turn the heat to low, cover the pot, and cook the cornmeal for 30 minutes, stirring every 10 minutes or so. The stirring is important to cook the mixture evenly without burning it.
3. Remove from the heat and add the margarine and nutritional yeast, then stir until combined.

For the Mushrooms:

1. While the polenta is cooking, wash and quarter the mushrooms. Heat the oil in a large skillet over medium-high heat and add the mushrooms. Cook, stirring often, until they begin to release their moisture, about 4-5 minutes.
2. Add the sherry and herbs, stir well, and let cook until most of the moisture has boiled off, about 4-5 minutes. Stir every now and then.
3. When the mushrooms are done, add some freshly ground salt and pepper, to taste.
4. Serve the polenta and top with mushrooms and some extra fresh herbs.