Polenta Bites with Wild Mushrooms and Fontina
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 …