Preparation

• Mound the flours on a clean, preferably wood, surface, and form a well in the center. Break the eggs into the well; sprinkle in the ground fennel seeds and the salt, and beat lightly with a fork to combine. Mix the dough, and knead it into a smooth ball, adding more flour as needed if the dough is sticky, about 5 minutes. Cover with plastic wrap and let rest at room temperature for at least 30 minutes and up to 2 hours.
• Set up a pasta machine with the rollers on the widest setting, or use the pasta roller attachment for a stand mixer. Scatter a little semolina on the ball of dough and on the work surface around the machine. Cut the dough into quarters and wrap three pieces. Flatten the fourth piece with your hand or a rolling pin into an oval 3 to 4 inches long and 3 inches wide. Feed it through the rollers, then lay it on the work surface. Fold it into thirds, like a business letter, sprinkle with a little semolina if it’s tacky, and pass it through the rollers again. Repeat the folding and rolling process three or four more times to smooth out and compact the dough and give it an even rectangular shape.
• Move the roller setting to the next narrower notch, and feed the dough through twice, sprinkling it with semolina as needed. Continue to pass the dough through the rollers twice on each successively narrow setting until the strip is about 26 to 28 inches long and 1/16 inch thick (I stop after running the dough once through setting #5 on my pasta machine). The strips should be thin enough to just see the shadow of your hand, but not so thin that they tear easily. Lay the strip on a semolina-dusted surface, and roll out the remaining pieces of dough in the same way. Cut the strips in half crosswise to yield eight 12- to 14-inch sheets. Let the sheets dry slightly.
• Cover a large rimmed baking sheet with a clean kitchen towel, and sprinkle it with semolina flour. Sprinkle the pasta sheets generously with semolina, and roll them up loosely, cigar-style, on the work surface. Use a sharp knife to cut the rolled sheets into 3/4-inch-wide noodles. Alternatively, use the pappardelle cutter attachment for a pasta machine to cut the sheets into pappardelle.
• Unroll the strips after cutting. Then wrap the noodles into loose nests and lay them on the semolina-dusted baking sheet. Cover loosely with plastic wrap. If not using within an hour or two, place the baking sheet in the freezer until the noodle nests are firm. Transfer the nests to a tightly lidded container, and store in the freezer until cooking time. To cook, transfer the pasta directly from the freezer to the pot of boiling water; do not thaw.