In medium saucepan, bring water and salt to a boil. Slowly whisk in polenta or cornmeal, making sure to remove any lumps. Turn heat to low, and cook uncovered for 25 to 30 more minutes, stirring every few minutes until it thickens and begins to pull away from the sides of the pan. For creamier polenta, add a splash more water. When done, remove from heat and stir in Parmesan and butter, if using.

Meanwhile cook mushrooms. In large cast iron frying pan, heat 1 Tbsp grapeseed oil over medium heat until shimmering. Add half the mushrooms and sauté over medium heat until golden, about 5 minutes. Transfer to bowl. Repeat with another 1 Tbsp oil, adding shallots and garlic along with remaining mushrooms, and sauté until mushrooms are golden. Transfer to bowl with first batch of mushrooms.

Deglaze pan with wine or water, scraping base of pan. Add rosemary and cook over medium heat until liquid is reduced by half, about 1 minute. Add stock and bring to a brief boil and cook until reduced to a thin sauce, about 4 minutes. Whisk in balsamic. Return mushrooms to pan, folding in until glazed. Season to taste with additional balsamic, salt, and pepper, if you wish. For extra glossy richness, stir in butter.

To serve, spoon creamy polenta into shallow serving bowls and top with braised mushrooms. Drizzle with some extra-virgin olive oil, if you wish. Season and garnish as desired.