Pasta

• 1¼ cup unbleached all-purpose flour
• ¼ teaspoon salt   
• 3 large eggs, plus 1 yolk
• 1 tablespoon extra-virgin olive oil

Filling and Sauce

• 2 tablespoons extra-virgin olive oil
• 1 small onion, finely chopped
• 2 heads radicchio, cored and thinly sliced
• ½ cup water
• ¼ teaspoon salt
• Freshly ground black pepper
• 6 ounces fresh robiola cheese, cut into 30 cubes
• 3 tablespoons unsalted butter
• 1 medium shallot, minced
• ⅓ cup pine nuts
• 3 tablespoons finely chopped fresh chervil
• ½ cup freshly grated Grana Padano cheese

For The Pasta: In a large mixing bowl, whisk together flour and salt. Mound flour mixture, create a well in center, and add 3 eggs, egg yolk and oil. Using a fork, gently break up yolks and slowly incorporate flour from inside rim of well. Continue until liquid is absorbed (about half of the flour will be incorporated), then knead in bowl until dough forms a complete mass. Transfer dough to a clean work surface and knead 8 to 10 minutes more. Wrap dough tightly in plastic and let rest for 30 minutes.

For The Filling And Sauce: In a large skillet, heat oil over medium heat. Add onion and cook until softened, about 3 minutes. Add radicchio, water, salt and pinch pepper. Cover, reduce heat to medium-low, and cook, until radicchio is very tender, about 15 minutes. Uncover, increase heat to medium-high, and cook until liquid is evaporated, about 1 minute. Remove from heat.

Divide dough into 4 balls. Cover with a lightly dampened towel. On a lightly floured surface, working with 1 ball at a time, roll out dough into very thin, flat sheets, about ⅛-inch thick. Put dots of 1½ teaspoons filling, set back 1 inch from edge of dough, onto dough, 2½ inches apart. Top each mound of filling with a cube of robiola. Bring outside edge of dough over filling to create a filled tube. Using a fluted pastry wheel, trim tube at the joined edges and at both ends, then cut tube between mounds of stuffing into squares. With a finger dipped in cold water, press down edges of squares to seal. Spread squares onto clean, dry dishtowels, making sure they do not touch. Repeat with remaining ingredients.

Bring a large pot of salted water to a boil. 

In a large, high-sided skillet, combine butter and shallot; cook over medium heat until shallot is softened, about 2 minutes. Stir in pine nuts and chervil, and cook 1 minute more; remove from heat.

In batches of ten, cook tortelloni in boiling water, until tender and floating at the top, about 2 minutes. Using a slotted spoon, transfer to a colander to drain. When all tortelloni are cooked, transfer to skillet with sauce; warm over medium heat, tossing gently to coat. Serve immediately with Grana Padano.