Polenta with Mushrooms and Cheese

First, make the sauce: If using dried porcini, place in a bowl with the hot water to cover and let soak until softened, about 1 hour. Remove the porcini, squeezing out the excess water, and chop finely. Line a small sieve with cheesecloth, place over a small bowl and pour the liquid through it. Set the mushrooms and liquid aside separately.

In a large sauté pan over medium heat, warm 2 Tbs. of the olive oil. Add the onion and sauté, stirring occasionally, until tender, 8 to 10 minutes. Remove from the pan and set aside. In the same sauté pan over high heat, warm the remaining 2 Tbs. oil with the butter. Add the fresh mushrooms and sauté until softened, about 8 minutes. Return the onion to the pan and stir in the garlic and sage. Sauté until fragrant, about 1 minute. Add the chopped dried mushrooms and the soaking liquid, if using, and cook, stirring, for 2 minutes to blend the flavors. Season with salt and pepper. Remove from the heat and keep warm while you cook the polenta.

To make the polenta, in a heavy saucepan over medium heat, combine the cornmeal, the 1 tsp. salt and the water. Bring to a simmer, stirring often, and then cook, stirring and scraping the bottom of the pan often, until thick and smooth, about 30 minutes. If the polenta thickens too quickly but still feels undercooked and grainy, stir in a little hot water and keep stirring over medium heat until cooked through and soft. Season with salt and stir in the butter and mascarpone cheese.

To serve, reheat the mushroom sauce. Spoon the polenta onto a warmed serving platter or individual plates. Top with the mushroom sauce and sprinkle with the Parmigiano-Reggiano cheese. Serve immediately.