You will need a pasta-rolling machine; a rotary pastry cutter or pizza wheel; a narrow pastry brush; trays or baking sheets lined with floured parchment or kitchen towels. To make the filling: Stir together the ricotta, fontina, grated cheese, and nutmeg in a large bowl. In a small bowl, beat the eggs with the salt, pour them over the cheeses, and stir everything with a wooden spoon until thoroughly blended and smooth. Cut the dough in six equal pieces. You’ll make tortellini from one piece at a time; keep the others covered. Roll the first piece through the pasta machine at progressively wider settings, always keeping it lightly floured, until you’ve created a long strip, as wide as your machine allows, and a little less than ⅛ inch thick. Lay out the strip on a lightly floured surface and, with the fluted cutter, cut it lengthwise in thirds, to form three long narrow strips, each about 2 inches wide. Cut vertically through the strips at 2-inch (or smaller) intervals, forming small squares of pasta. You should have thirty or more squares in all. Remove excess bits of dough (which can be kneaded together, rested, and rerolled for more pasta).

Place a scant teaspoon of the filling in the center of each square. With the pastry brush (or your fingertip) dipped in water, lightly moisten the edges of the squares around the filling. To form each tortellino: Pick up one square and fold it over on the diagonal, creating a triangle with the filling inside; press the moistened edges together to seal it well. Next, grasp in your fingers the corners of the base of the triangle (its long side), twist them inward so the points of dough overlap, and pinch them together. As you make the twist, the stretching of the dough will make the fluted edges and the opposite point of the triangle will pop up, creating the plump hatlike tortellini shape.

Fold and twist the rest of the squares into tortellini; set them in a single layer on a lined and floured tray. Make more tortellini from the other cut pieces of dough (and the rerolled scraps of dough, too). Tortellini that you will cook soon can be left on the tray, lightly covered. Freeze tortellini for future use right on the trays until solid, then transfer them to freezer bags, packed airtight and sealed. To cook and serve tortellini with marinara sauce for four, you will need seventy to eighty tortellini (eighteen to twenty per serving, depending on pasta size and your guests’ appetites). Fill a large pasta pot with well-salted water and bring to the boil. Pour the Marinara Sauce into a large skillet or sauté pan (at least 12 inches in diameter); heat sauce to a simmer when you start cooking the pasta. Drop all the tortellini into the rapidly boiling water at once, stir, and return to the boil over high heat.

Cook for about 3 minutes (longer if frozen), until the thickest part of the pasta is cooked through and slightly al dente. Lift them from the cooking pot with a spider, drain briefly, and lay them in the simmering sauce. Tumble the tortellini over and over for a minute or so, until all are coated and perfectly cooked. (Loosen the sauce, if it is thick, with hot pasta water, or thicken it quickly over higher heat if necessary.) Turn off the heat, sprinkle a cup or so of grated cheese over the tortellini—and a flourish of extra- virgin olive oil if you like—and toss gently. Spoon the tortellini into warm bowls, and serve immediately, with more cheese at the table.