Polenta Cakes with Quick Sausage Sauce

Name: Polenta Cakes with Quick Sausage Sauce
Ingredients: 1 cup milk; 2 cups water; 1 bay leaf; Pinch cayenne pepper; Kosher salt; 1 cup polenta; 4 fresh sage leaves, finely chopped; 1/4 cup mascarpone; 4 tablespoons grated Parmigiano-Reggiano, plus more for serving; Half recipe Italian Sausage, recipe follows; 1/2 onion, peeled and diced; 1/2 fennel bulb, diced; 1 celery rib, diced; 1 clove garlic; Pinch crushed red pepper flakes; Extra-virgin olive oil; 1/2 cup tomato paste; 1/2 cup white wine; 2 cups tomato puree; 2 pounds pork shoulder (with a good amount of fat), cut into large chunks; 2 cloves garlic, minced; 2 tablespoons kosher salt; 1 tablespoon fennel seed; 1/2 tablespoon crushed red pepper; 1/2 tablespoon ground coriander; Ice cold water; Oil; Hog casing; Special equipment: stand mixer with meat grinder and sausage horn attachments