Prepare the Polenta by bringing water or vegetable broth to a boil. Gradually whisk in the polenta and cook until thick and creamy, about 10-15 minutes.

Sauté the mushrooms in a large skillet with olive oil over medium heat, seasoning with salt and pepper, until tender and golden brown for 8-10 minutes.

In a large bowl, combine the cooked polenta, sautéed mushrooms, and cheese, mixing with a splash of vegetable broth if desired.

Layer the polenta mixture in a greased casserole dish, adding extra cheese or sautéed vegetables if desired, then top with remaining polenta.

Bake the casserole in a preheated oven at 375°F (190°C) for 30-40 minutes until the top is golden brown.

Cool the casserole for 5-10 minutes before serving to allow flavors to meld.