4 tablespoons (1/2 stick) butter, divided
4 hot Italian sausages, casings removed
1 small onion, chopped (about 1 cup)
2 small bay leaves
1 cup arborio rice or medium-grain white rice
1/2 cup dry white wine
3 cups (or more) low-salt chicken broth
Pinch of saffron threads
1/3 cup freshly grated Parmesan cheese plus additional for serving
1/3 cup chopped fresh Italian parsley