Ingredients:
Pasta & Filling
4 yellow onions (about 2 pounds), halved, peeled, and thinly sliced
30 milliliters(2 tablespoons) extra-virgin olive oil
Kosher salt and freshly ground black pepper
2 sprigs fresh thyme
2 springs fresh rosemary
6 sage leaves
55 grams(4 tablespoons) unsalted butter, cut into small pieces
15 milliliters(1 tablespoon) aged sherry vinegar or balsamic vinegar
120 grams(½ cup) whole-milk ricotta
50 grams(1½ to 2 ounces; about ¾ cup) grated smoked mozzarella or scamorza
300 grams(about 2½ cups) ’00’ pasta flour or all-purpose flour
50 grams(about ¼ cup) semolina or semola rimacinata flour (optional; if unavailable, use the same weight in ‘00’ or all-purpose flour)
200 gramseggs (about 4 large eggs), beaten
Semolina flour or cornmeal, for dusting
Broth
225 grams(4 to 5 large) Parmigiano-Reggiano rinds
2 garlic heads
1 large yellow onion
30 milliliters(2 tablespoons) extra-virgin olive oil
1 large or 2 medium carrots, roughly peeled and cut into 1½-inch pieces
2 celery stalks, trimmed, cleaned, and cut into 1½-inch pieces
5 sprigs fresh thyme
5 sprigs fresh parsley
2 dried bay leaves
5 grams(2 teaspoons) black peppercorns
Kosher salt, to taste
Parmigiano-Reggiano, for serving (optional)
Directions:
Make the filling: Heat the oven to 400°F. In a 9×13-inch baking dish, toss the onions with the olive oil, herbs, and a generous dusting of salt and pepper until well coated. Scatter the butter cubes and herbs on top of the onions. Roast until very tender and amber in color, about 90 minutes, stirring every 20 minutes. (While the onions roast, make the pasta dough and start the broth.)
Remove the herb sprigs, as well as any scorched onion pieces. Stir in the vinegar and adjust the seasoning to taste. Allow to cool.
Combine the cooled onions, cheeses, and a generous pinch each of salt and pepper in a food processor fitted with the steel blade attachment. Pulse until well combined, about 1 minute. Adjust the seasoning to taste, then transfer to a piping bag or bowl and refrigerate until chilled and ready to use, at least 30 minutes.
Storage note: Leftover filling can be refrigerated in an airtight container for up to 3 days. (It’s great as a pasta sauce or a dip with crackers!)
Make the pasta dough: Make the pasta dough by hand according to the well method (see Author Notes).
Alternatively, add the flour and eggs to the bowl of a stand mixer fitted with the dough hook. Mix on low speed, scraping down the sides of the bowl as needed, until the mixture comes together, about 7 minutes. Transfer the dough to a flat, ideally wooden work surface and knead for 2 to 3 minutes, until smooth and firm.
Wrap the dough tightly in plastic and allow it to rest at room temperature for at least 30 minutes and up to 2 hours. If rolling by hand, let rest for at least 1 hour.
Roll the pasta sheets: Line a sheet pan with semolina flour, cornmeal, or a dry dish towel and keep it nearby. Cut off a quarter of the dough and rewrap the remainder immediately.
If using a pasta machine: Flatten the dough with the heel of your hand until it’s about ¼ inch thick. Set the pasta machine to its widest setting and roll the dough through once (it will be tapered at the ends). Fold both ends into the center like an envelope, so the width of the pasta sheet is similar in width to the pasta roller. Roll the dough through the widest setting once more so the result is an even rectangle.
Continue rolling the pasta sheet through the machine once on each progressive setting until you have a very thin sheet (about setting 7 on a Marcato Atlas 150 manual roller or setting 6 twice through the KitchenAid attachment). If the dough is at all sticky as it goes through the machine, dust both sides with a little ‘00’ or all-purpose flour.
If rolling by hand: Roll a portion of dough with a rolling pin into a thin, rectangular sheet that’s about 6 inches wide (the length will vary depending on the amount of dough you use). While you’re aiming for about a millimeter thick, don’t stress and just do the best you can.
Assemble the tortelli: Once you have a long, almost-transparent sheet of pasta, lay it on a wooden surface and trim any uneven edges (ball up the scraps and wrap them in plastic to rehydrate—they can be rerolled at the end). If you don’t have a wooden surface, dust a little flour on the bottom of the pasta sheet and your countertop to prevent sticking.
Fold the pasta sheet in thirds lengthwise. Gently create creases at each fold and unfold the pasta sheet. You should see the outline of three even rows. With a sharp knife or pasta wheel, cut the sheet along each seam, then cut the rows crosswise into squares (they should be about 4½ centimeters/1¾ inches). Alternatively, use a bicycle pastry cutter.
Spoon or pipe a small dollop of the chilled filling in the center of each square, leaving about a ½-inch border of dough around it.
Fold each square into a triangle, meeting opposite points first and then gently pressing out any air around the filling on each side. Once the filling is encased, go back over the edges with your fingers and press firmly to seal.
Position the triangle so the top point is facing downward. Then use your index finger to gently make an indentation on the top edge of the pocket. Bring the two side points of the triangle together over the indentation, overlap them slightly, and pinch firmly to seal (see process images above).
Place each finished piece on the prepared baking sheet in a single layer. Repeat the process with the remaining dough. To help prevent the dough from drying out, start by filling only a few squares at a time and cover the rest of the dough with a clean, lightly damp dish towel.
Storage note: To store the tortelli for future use, freeze them in a single layer on the sheet pan until mostly solid, about 25 minutes (you might need to do this in batches), then transfer them to a freezer-safe container or bag—they’ll last for up to a couple of months. When you’re ready to cook them, boil straight from frozen until tender, about 3 to 3½ minutes.
Wrap the cheese rinds in cheesecloth and tie a knot at the top. This will prevent the cheese from sticking to the pot as it cooks; if you don’t have cheesecloth, skip this step but make sure to stir the broth occasionally to prevent sticking.
Cut the tops off the garlic heads crosswise so most of the cloves are exposed. Halve the onion through the root and leave the skin on.
In a large Dutch oven or 8-quart stockpot, heat the olive oil over medium-high. Add the garlic and onions, cut side down, and cook until slightly caramelized, 2 to 3 minutes.
Add the wrapped cheese rinds, carrot, celery, herbs, and spices to the pot, as well as about 4 quarts water, or enough so that everything is submerged.
Bring to a boil, then immediately reduce to a bare simmer. Cook the broth until golden in color and reduced by half, about 2 to 2½ hours. When it’s done, strain through a fine-mesh sieve into a medium saucepan, pressing as much liquid as possible from the vegetables and cheese rinds, and season to taste with salt.
Storage note: The cooled broth can be stored in the refrigerator for up to 1 week and the freezer for up to 3 months. Skim the fat off the top once it’s cool, if you’d like.
For serving: Bring a large pot of water to a gentle boil and season it generously with salt. Bring the strained broth to a low simmer.
Carefully add about 25 tortelli per serving to the water (freeze the rest for another use), shaking off any excess flour, and cook until almost tender, about 2 minutes. Transfer the pasta directly to the broth with a spider or slotted spoon. Simmer gently for 1 minute more (it’s fine if the pot is a bit crowded).
Divide the pasta and broth among bowls. Serve immediately, topped with shavings of Parmigiano-Reggiano, if you’d like.