If you're looking to impress your friends, which I almost always am, give this a whirl. Think of it this way: you're deconstructing and re-constructing an egg, replacing the white with a ricotta-based filling, and the shell with a shell of pasta. In this recipe, a little diligence and a lot of care goes a long way. —Hi, I'm Brian.
In the bowl of a food processor, combine the flour and salt. Pulse once or twice to mix it together. Then add the eggs one at a time, pulsing between each egg to break it up and fully incorporate it into the flour.
Once all the eggs have been added and the dough resembles coarse sand, turn it over into a large bowl. The bowl is optional, but it helps keep the mess contained. Form the dough into a ball and knead until it starts to feel soft and silky, about 5 minutes. Wrap in plastic and refrigerate for at least 30 minutes.
In a medium sized bowl, mix together the ricotta, Parmesan, lemon zest, truffle oil, nutmeg, salt, and pepper. Set aside.
Remove the pasta from the refrigerator and using a pasta roller, roll it out to the second thinnest setting. Cut the pasta into 24 4-inch rounds. The size here is important. Too small and the ravioli will be impossible to handle without breaking the yolk during assembly.
Place about 1 tablespoon of filling into the center of a pasta round and work it into a crater that will accommodate the egg yolk. Carefully place the yolk into the crater, wet the outer edge of the pasta round, and place a second pasta round on top. Carefully seal the ravioli. Place on some floured parchment paper. Repeat 11 more times to make 12 ravioli.
Bring a large pot of unsalted water to a boil over high heat.
Meanwhile, heat a large saucepan over medium-high heat and cook the pancetta until it begins to brown, about 5 minutes. Reduce the heat to medium and stir in the shallots. Stirring constantly, cook until the shallots are soft and translucent, about 5 minutes. Add the butter to the pan, and once it's melted add the white wine. Bring to a simmer and cook until slightly reduced, about 10 minutes. Stir in the lemon juice and remove from heat.
By this point the water should be boiling. Add the ravioli to the pot and partially cover. This is because adding the ravioli will reduce the heat, but we want to keep it as hot as possible. Cook the ravioli for no more than 3 minutes, stirring periodically to submerge because the ravioli will bob to the top.
Once the ravioli is cooked, divide among 4 plates. Spoon over the sauce and garnish with parsley. Serve.