1. In a large pot, combine 5 cups water, the broth, coarsely chopped shallot and porcini mushrooms; bring to a boil over medium-high heat. Remove from heat, cover and let stand 30 minutes. Lightly moisten cheesecloth with water, fold into a double layer and place in a fine-mesh sieve set over a large bowl. Pour mushroom stock through cheesecloth; remove and rinse porcini mushrooms (discard shallot). Rinse pot and return strained stock to pot; set aside. Finely chop porcini mushrooms.
2. While stock is standing, trim and clean assorted mushrooms; slice and reserve 1 cup. Finely chop remaining mushrooms.
3. For ravioli filling, in a medium nonstick skillet, melt butter over medium-high heat. Add porcini and chopped mushrooms, remaining shallot and the garlic. Saute, stirring occasionally, until shallots are translucent and mushrooms are softened, about 6 minutes. Remove from heat and transfer to a bowl. Let cool slightly, about 10 minutes. Stir in cheeses, parsley and thyme; salt and pepper to taste.
4. For ravioli, place 1 tablespoon filling on one side of each wonton wrapper. Brush two opposite edges with water and fold over to form a triangle. Press firmly to seal.
5. For soup, bring stock to a boil; add reserved mushrooms and the ravioli. Cover and cook until just tender, 3 to 4 minutes. Ladle into bowls and garnish with parsley, if desired. (Freeze soup and uncooked ravioli separately in airtight containers up to 1 month. Store ravioli in single layers separated by waxed paper.) Makes 12 cups.