Separate stems of chard from leaves. Dice stems, and coarsely chop leaves. You should have about 3 cups packed leaves.
In a medium skillet, melt butter over medium heat. Add shallot, and cook, stirring, until translucent, about 30 seconds. Add chard leaves, 3/4 teaspoon thyme leaves, salt and pepper to taste. Cook, stirring, until completely wilted, about 2 minutes. Transfer to a medium bowl, and refrigerate until cool, about 5 minutes. Stir in ricotta and Parmesan. Season, to taste.
In a small saucepan, combine stock, 1 sprig thyme, and chard stems. Bring to a boil. Lower heat to a simmer, and cook for 3 minutes. Remove from heat. Let stand until the liquid is dark pink, 5 to 10 minutes. Strain through a sieve, season with salt and pepper; set aside.
Place 12 wonton wrappers on a clean work surface. Mound a slightly heaping tablespoon filling in center of each wrapper, brush edges with beaten egg. Top each square with a second wrapper. Press edges together to seal.
Bring a large pot of water to a boil. Add salt. Working in batches, add ravioli. Cook until the ravioli are translucent and have risen to the surface, 1 to 2 minutes. Meanwhile, ladle about 1/4 cup broth into each of 4 shallow bowls. Using a slotted spoon, remove ravioli, placing 3 in each bowl. Garnish with remaining thyme leaves.
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