Preheat your oven to 450°F. Separate oyster mushrooms into bite-sized pieces and place them in one layer on a large, rimmed cookie sheet. Toss with olive oil and sea salt to taste. Roast for about 15 minutes, or until browned and crispy, flipping mushrooms halfway through.

In a medium saucepan, bring water to a boil. Whisk in cornmeal, being sure to get rid of any lumps, and lower heat to a simmer. Add a tablespoon of butter and a ½ teaspoon of salt. Cover and cook for 5 to 10 minutes, or until polenta is thickened and soft, stirring often. Take off heat, stir in goat cheese, and season to taste.

To make the brown butter, melt the remaining butter in a small saucepan over medium heat. Add rosemary once the butter starts to foam. Immediately take off heat when milk solids start to turn brown, like a chestnut color. Discard rosemary.

To plate, ladle polenta into warmed bowls. Top off with roasted mushrooms and drizzle brown butter on top. Finish with grated Parmigiano Reggiano cheese and serve immediately.