Special equipment: pasta cutter
Mound the flour on your work surface. Make a well and add the eggs to the center. Use a fork to whisk them together. Once blended, keep whisking the eggs, slowly incorporating the edges of the flour. Use your hands to fold the eggs and flour all together. While the dough is still loose, drizzle in the oil and a half-eggshell of cold water (about 2 tablespoons) and keep kneading until smooth, elastic and warm. Wrap the dough in a clean kitchen towel and let it rest while you make the filling.
Combine the ricotta, Parmesan, sage, thyme, mint and nutmeg in a large bowl and add salt and pepper to taste.
To assemble: Cut the dough into 4 equal pieces. Roll the dough through the pasta machine beginning at the thickest setting and working your way down to the thinnest. You want the pasta about 1/4-inch thick and in a long rectangular sheet. Repeat with the remaining dough.
Flour your work surface. Trim the edges of the pasta sheets with a pasta cutter to make the sheets even. Drop about 1 scant tablespoon of the filling onto one half of a pasta sheet, leaving a 2-inch space between the next drop of filling. Brush the edges lightly with water. Fold the dough over the filling, like closing a book. Use your fingers and the side of your hand to press the seams between each filling mound and seal them closed. Seal the edges. Use a pasta cutter to trim the mounds into ravioli. If making the ravioli ahead of time, toss them with some semolina flour so they do not stick together.
To finish: Melt the butter in a large saute pan. Add the sage leaves and truffles and cook until just crisp and fragrant, about 2 minutes.
Bring a large pot of water to boil. Cook the ravioli in batches, about 10 at a time, until they float to the surface, 2 to 3 minutes. Toss the ravioli with the melted butter mixture, add some Parmesan and shave some fresh truffles on top.