Roast the onions for the broth by chopping 2.2 pounds/1 kilogram white onions into large chunks. Spread them on a roasting tray with a drizzle of olive oil, fresh sage leaves, thyme, and 1 cup dry white wine. Roast in a 400°F/200°C oven for 25–35 minutes, turning occasionally, until deeply golden and caramelized. This step builds the sweet, rich base of the onion broth.

Prepare the onion broth by transferring the roasted onions and wine to a large pot. Add 4 cups/960 ml water and a pinch of salt. Simmer gently for 2–3 hours to fully extract flavor. Blend until smooth, then strain through a fine-mesh sieve. Return the liquid to the pot and reduce over low heat until concentrated and aromatic. Season to taste.

Make the pasta dough by combining 2 ½ cups/300 grams 00 flour and a pinch of salt in a large mixing bowl. Form a well in the center and add 7–8 egg yolks/135–150 grams. Mix until a rough dough forms, then knead for 10–15 minutes until smooth, elastic, and slightly tacky. Wrap tightly in plastic wrap and chill for 30–45 minutes to relax the gluten.

Prepare the filling by mixing 1 cup/250 grams drained ricotta, ½ cup/120 grams mascarpone, ¼ cup/60 grams finely grated Parmesan, and truffle paste or finely shaved fresh truffles to taste until smooth and creamy. Transfer the mixture to a piping bag and keep chilled until ready to assemble.

Assemble the tortellini by rolling the chilled dough thin using a pasta machine or rolling pin. Cut into squares about 2 inches/5 cm wide. Pipe a small amount of filling into the center of each square, fold into a triangle, then bring the corners together to seal into a tortellini shape. Press firmly to remove air pockets. Freeze or refrigerate until ready to cook.

Cook and finish the dish by bringing a large pot of salted water to a gentle boil. Cook the tortellini for 3–4 minutes until tender and floating. Drain carefully and transfer to a skillet with the warm reduced onion broth and 2 tablespoons unsalted butter, tossing gently to coat without breaking the pasta.

Final tip: Warm ½ cup heavy cream with 2 tablespoons mascarpone and a pinch of salt over low heat to create the truffle cream. Spoon over the tortellini and finish with grated Parmesan, dried onions, and shaved truffle. Drizzle lightly with truffle oil just before serving to enhance aroma.