Sauté until the sausage is brown on the outside but still pink in the center, then add half the ground fennel and half the red-pepper flakes. When the sausage pieces are just cooked through ...

In a large skillet, cook the Italian sausage and ground beef over medium heat, crumbling the meat with a spatula, until beginning to brown. Add the chopped onion and cook until meat is no longer ...

Add the sausage and cook over high heat, breaking up the meat with a spoon, until browned, about 5 minutes. Add the fennel and cook, stirring occasionally, until softened and lightly browned ...