Bring a large pot of salted water to a boil. In a heavy saute pan, add chicken stock, chopped sage, and butter. Boil until mixture emulsifies. Season with salt and pepper.
Cook the agnolotti in the water until al dente, about 2 to 3 minutes. Remove with a slotted spoon and toss gently in the sage butter. Serve in soup plates and shave white truffles on top.
To take advantage of the wonderful truffle aroma, cover each individual bowl of agnolotti with another plate. When brought to the table, remove the top plate so that the truffle aroma escapes just as the guest takes the first bite.
In a medium saute pan, bring the cream to a boil. Reduce until only 1/3 cup remains. Stir in the grated corn, salt, pepper and sugar. Bring the mixture to a slow boil, stirring constantly. Continue to cook until the mixture reduces and thickly coats the back of a spoon.
Transfer mixture to a medium bowl. Stir in the cheeses and thyme and mix until well blended. Taste and adjust seasoning with salt and pepper. Place bowl over ice bath to allow filling to set.
Make the agnolotti: Roll out the dough very thin. Brush with eggwash. Mound little heaps of filling about 1-inch apart. Fold over and squeeze dough together in between filling mounds. With a serrated pasta cutter, cut agnolotti. Cut away excess dough lengthwise; there should be no more than 1/4-inch around the edges.
Yield: about 2 cups of filling, makes about 100 agnolotti
In a food processor fitted with the steel blade, combine the flour, egg yolks, salt, olive oil, and 2 tablespoons of the water. Process until the dough begins to hold together, then stop the machine and pinch the dough to test it. If it's too dry, add up to 1 more tablespoon of water and process until it forms a moist ball. Turn out onto a lightly floured smooth work surface and knead by hand, until a smooth ball is formed. Loosely wrap in plastic and let rest at room temperature for 30 minutes to 1 hour.
Cut the dough into 4 equal pieces. Keep the other pieces covered in plastic while you roll out one piece at a time, by hand with a rolling pin or through the rollers of a pasta machine, stretching the dough to the desired thickness.
If using a pasta machine, set the rollers at the widest opening. Flatten the first piece of dough into a thick strip no wider than the machine, to enable it to pass through the rollers. If necessary, dust the pasta very lightly with flour. Run the pasta through the machine. Fold in thirds, crosswise, and run through the machine again. Repeat this procedure 2 more times, until the dough is smooth and somewhat elastic.
Set the machine to the next smaller opening and run the dough through the rollers. Continue rolling and stretching the dough, using the smaller opening each time, until the next to the last or the last opening is reached, dusting lightly with flour only as necessary. (The strip of dough will be long. If you don't have enough space on your worktable, halfway through the rolling process, cut the strip of dough in half and continue to work with each piece separately, keeping the unused dough covered).