Chef Scott Conant makes Taleggio Mezzaluna with taleggio cheese and fresh pasta dough.
Watch Scott demonstrate how to make fresh pasta using a pasta maker here.
In a stand mixer fitted with the paddle attachment, combine the Taleggio and mascarpone on medium speed until smooth, about 3 minutes. You want to be sure the cheeses are well-homogenized before adding the egg (don't worry; you can't over mix).
Add the yolk and mix until well-combined, then add the truffles and mix briefly to combine. (The filling may be made up to 2 days ahead and kept covered and refrigerated. Let it come to room temperature before using.) Transfer the filling to a pastry bag fitted with a plain 3/8- or 1/2 inch tip.
Roll the pasta out into sheets; strive for the thinnest setting on your machine but if the dough starts to tear, the second-to-last setting is fine.
Lightly flour a rimmed baking sheet. Cut the sheets of dough lengthwise into 2 1/2 inch strips. Work with one strip at a time, and keep the others covered with plastic wrap to prevent them from drying out. Very lightly brush a little water over the entire strip. Pipe about 1/2- teaspoon dollops of filling at 2-inch intervals just a little bit above the middle of the strip. (Alternatively, use a small spoon to drop the filling onto the strip.)
Lift the bottom edge of the strip and bring it to meet the top, letting it fall loosely over the filling. Using the pinky side of each hand gently pat them close to each mound of filling to coax out any trapped air. Position a 2-inch round cookie cutter over the filling and folded edge of the dough so that one-third of the cookie cutter hangs below the folded edge and the filling is approximately centered. Press to cut shapes that are mostly round but with a straight bottom, like half- moons. Repeat to make more half-moons. As you work, transfer the filled pasta to the baking sheet in a single layer. Freeze the pasta on the baking sheet until hard; the freezing makes them easier to handle. Once they are rock-hard, you can transfer them to freezer bags or other airtight containers. (The mezzaluna will keep, frozen for up to 2 weeks.)