• 1¼ cup, plus 1 tablespoon unbleached all-purpose flour
• 1 tablespoon buckwheat flour
• Salt
• 2 large eggs
• ¾ cup grated gruyère cheese (about 2½ ounces)
• ¾ teaspoon white truffle paste
• Freshly ground black pepper
• 1 pound new potatoes
• 1 tablespoon extra-virgin olive oil
• 8 tablespoons unsalted butter
• 12 fresh sage leaves
• ⅓ cup freshly grated Parmigiano-Reggiano cheese

Whisk together all-purpose flour, buckwheat flour and pinch salt in a large bowl. Mound flour mixture and form a well in the center. Add eggs to well. Using a fork, gently break up yolks and slowly incorporate flour from the inside rim of the well. Continue until liquid is absorbed, then knead in bowl until dough forms a complete mass. Transfer dough to a clean work surface and knead until smooth and elastic, about 10 minutes more. Wrap dough tightly in plastic and let rest at room temperature for 1 hour.

Meanwhile, combine cheese, truffle paste and generous pinch salt and pepper in a large bowl. Bring a large saucepan of water to boil. Boil potatoes until tender, about 15 minutes. Drain and pass through ricer into bowl with cheese mixture; stir well to combine.

Divide dough into 3 pieces. On a lightly floured surface, roll out 1 piece to ⅛-inch thick (keep remaining pieces covered with plastic wrap to avoid drying out). Using a 4-inch cutter, cut 6 rounds from dough; knead scraps into remaining pieces.

Place about 1½ teaspoons potato filling on lower half of each round, leaving a border. Fold top half of each round over filling and press edges together to seal. Wrap edges of each half-circle around your index finger, bringing ends together to overlap by about ¼ inch. Pinch edges to seal. Place finished ravioli on a large plate and cover with a clean dishtowel; repeat with remaining dough and filling to make a total of about 25 ravioli.

Bring a large pot of water to a low boil; in batches, add ravioli and cook until tender, about 4 minutes. Using a slotted spoon, transfer to serving plates.

In a small saucepan or skillet, melt butter over medium heat. When butter becomes tawny gold in color (not yet brown) and foam subsides, add sage leaves. Cook a few seconds, remove from heat, and spoon over ravioli. Sprinkle with cheese and serve immediately.