Mushroom Soup with Chorizo and Scallions

Name: Mushroom Soup with Chorizo and Scallions
Ingredients: 4 tablespoons unsalted butter; 4 pounds large white button mushrooms (thinly sliced); 4 large shallots (thinly sliced); 1 garlic clove (smashed); 6 cups chicken stock or low-sodium broth; 6 cups water; 5 small thyme sprigs; 5 sprig parsley; ⅓ cup heavy cream; ¼ cup soy sauce; 1 tablespoon cornstarch dissolved in 2 s water; Salt and freshly ground pepper; ½ pound chorizo (peeled and coarsely ground in a food processor or); 1 tablespoon unsalted butter; ½ pound small white button mushrooms (quartered); 1 bunch scallions (about 6 white and green part, thinly sliced)