Special equipment: a pasta maker; a stamp cutter or pastry wheel
For the pasta dough: Mound the flour on a large work surface and form a well in the center with your fingers. Add the eggs, egg yolk, olive oil and salt to the well. Using a fork, lightly beat the wet mixture until combined. Then incorporate the flour, beginning with the inner edges of the well and working outwards, until a shaggy dough forms. Knead the dough by hand until completely smooth, 8 to 10 minutes. Wrap the dough in plastic wrap and let rest for at least 20 minutes. (It is important to let the dough rest; otherwise, the gluten in the flour will make it very difficult to roll out. The dough can be made a couple of days in advance and kept in the fridge.)
For the ravioli: Mix together the ricotta, Parmigiano and walnuts in a medium bowl. Add the nutmeg and salt and pepper to taste; mix again and set aside.
Cut the pasta dough into four equal pieces. Roll the first piece through a pasta machine on its widest setting. Decrease the width by one notch and roll the dough through again. Continue, decreasing the width one notch at a time (ending somewhere between settings 5 and 7, depending on your machine), until the pasta is very thin. Place the pasta sheet on a flour-dusted work surface. Repeat with the three remaining pieces of dough.
On one of the pasta sheets, place rounded balls of filling (about 2 tablespoons each) spaced 1- to 1 1/2-inches apart. Brush the pasta around each ball lightly with water. Lay a second sheet of pasta on top and press firmly around each ball, making sure there are no air pockets. Using a stamp cutter or pastry wheel, cut out each ravioli (about 2 inches in diameter) and transfer to a baking sheet lightly dusted with flour. Repeat with the remaining two sheets of pasta. I like to use a fork to press the edges of the ravioli to make sure they are closed and to give them a pretty design.
For the cream sauce: Melt the butter in a large skillet over medium heat. Add the garlic and fry until fragrant, 1 to 2 minutes. Add the walnuts and fry for 2 minutes more. Add the cream and mix well. Bring to a simmer, then reduce the heat to low and simmer gently until slightly thickened but still liquid, about 8 minutes. Season with pepper.
While the sauce is cooking, bring a large pot of water to a slow boil. Carefully lower half of the ravioli into the water. Cook until the ravioli start to float and are just tender, about 2 minutes. Using a slotted spoon, transfer the ravioli directly to the sauce. Repeat with the remaining ravioli. Sprinkle with the Parmigiano and gently toss to coat the ravioli in the sauce.
I like the walnuts very finely chopped so you can taste them but not feel them very much.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.