Combine the flour and egg yolk in a food processor. Process until uniform, dry crumbs form.

Melt mozzarella in the microwave or a double boiler on the stove, until easy to stir.

Add the mozzarella to the flour mixture and process again until a uniform dough forms. Scrape the sides and reposition dough over the blade as needed.

Form the dough into a ball. If it’s sticky, cover with plastic wrap and refrigerate for 30 minutes. Place the ball of dough between 2 large pieces of lightly greased parchment paper. Roll out the dough into a very thin rectangle, about 1/16 inch (0.16 cm) thick.

Peel off the top piece of parchment paper. Cut into narrow strips, about ¼ inch (.64 cm) wide, like fettuccine. Arrange slightly apart on the parchment paper.

Slide the bottom piece with the pasta onto a large baking sheet. Place in the refrigerator, uncovered, to dry out overnight, at least 8 hours, until noodles are stiff.

To cook pasta, bring a pot of water to a boil. Quickly drop in the pasta and let it cook for about 1 minute, until pasta floats in swirls. Be careful not to overcook, or they will disintegrate.