Four Cheese Ravioli
Dust a parchment-lined baking sheet with cornstarch. Brush the perimeter of a wonton skin with the beaten egg. Place about 1 heaping teaspoon of the filling in the center, and top with another wonton skin. Press firmly to seal the edges. Place on the baking sheet. Repeat with all the skins and filling, separating the layers of ravioli with parchment. (The ravioli can be prepared up to 8 hours ahead, covered with plastic wrap and refrigerated.)
Bring a very large pot of lightly salted water to a boil over high heat. Drop in the ravioli, stirring them occasionally to be sure they aren't sticking. Cook until the ravioli float to the surface, about 4 minutes.
Using a skimmer or wire sieve, scoop out the ravioli and divide them among soup bowls. Spoon about 1/2 cup of the hot soup into each bowl. Serve immediately, with the cheese passed on the side.