Ingredients

• 4 pounds prepared polenta, sliced into 1/2-inch-thick rounds (about 30 rounds)
• 2 tablespoons extra-virgin olive oil, plus more for brushing
• 1/4 cup (1/2 stick) unsalted butter
• 2 pounds assorted wild mushrooms (such as oyster, crimini, and/or stemmed shiitake), cut into thick slices
• 2 shallots, thinly sliced
• 1/4 cup Sherry vinegar
• 1 3/4 teaspoons kosher salt
• 1/2 teaspoon freshly ground black pepper
• 1/2 teaspoon crushed red pepper flakes
• 1/2 cup chopped parsley leaves
• 4 ounces Fontina cheese, coarsely grated (about 1 cup)

Instructions

1. Preheat oven to 450°F. Brush both sides of polenta slices very lightly with oil and arrange on 2 rimmed baking sheets. Roast polenta until lightly golden brown and warmed through, about 25 minutes.
2. Meanwhile, melt butter with remaining 2 Tbsp. oil in large, deep skillet over medium-high heat. Add mushrooms and cook, stirring often, until tender and browned, about 12 minutes. Add shallots, vinegar, salt, black pepper, and red pepper and cook, stirring, until tender, about 5 minutes. Stir in parsley.
3. Divide mushroom mixture between baking sheets with polenta. Top with cheese. Continue to roast until cheese is melted, about 5 minutes.
4. Arrange polenta bites on a platter and serve.
5. Mushroom mixture can be made 1 day ahead. Transfer to an airtight container and chill.