Creamy Polenta with Charred Onions and Black Trumpet Mushrooms
For the polenta
4 cups reserved leek blanching liquid, stock, or water
1 cup course-ground cornmeal or grits
2 tablespoons butter
¼ cup cream
¼ cup grated Parmesan cheese, optional
For the mushrooms
3 tablespoons butter, divided
3 tablespoons olive oil, divided
2 small onions, sliced into rounds
1 garlic clove, minced
2 cups fresh or frozen black trumpet mushrooms
1 teaspoon fresh thyme leaves
To make the polenta, bring liquid to a rolling boil and stir in cornmeal or grits. Reduce heat and simmer, stirring regularly, until cornmeal is completely softened, 20–40 minutes depending on how finely ground the cornmeal or grits are. When cornmeal or grits are cooked, stir in butter, cream, and Parmesan cheese, if using. If not using the cheese, you may need to season the polenta with salt.
To prepare the mushrooms, combine 2 tablespoons each butter and olive oil in a wide skillet. Place over medium high heat. When butter is melted, add onions so they lie flat in the pan. Let them cook undisturbed until they are slightly charred, about 7 minutes. Reduce heat, flip onions over, and cook until they are softened, another 10 minutes. Transfer to a warm plate.
Wipe out skillet. Combine remaining butter and oil. Place back over medium heat. When butter is melted, add garlic and cook for 30 seconds. Add mushrooms, stir and cook until mushrooms soften, 4–6 minutes. Season with salt and stir in thyme leaves. Keep warm until polenta is cooked.
To serve, ladle polenta into bowls and top with charred onions and sautéed black trumpets.