These stuffed portobello “tartlets” are endlessly versatile, as roasted portobello caps are the perfect vessels for all sorts of toppings. I have stuffed them with creamy scrambled eggs for an elegant brunch, tomato sauce and mozzarella for a take on pizza, and ground veal and béchamel for an elegant first course. In this recipe, I use ground sausage mixed with vegetables, topped with a layer of melted cheese. I use fontina cheese, as I love its distinct sharp flavor and how it melts, but Swiss, Munster, or even manchego work, too. Just make sure you use a semi-soft cheese, so it will melt beautifully. Serves 4 4 large portobellos, cleaned and stems removed 6 tablespoons olive oil, divided 1 small onion, finely diced (about 1/2 cup) 1 stalk celery, finely diced 2 cloves garlic, minced 3/4 pound ground sausage meat, mild or hot 1/2 cup grated Parmesan 4 ounces fontina …