Heat olive oil in a large casserole or heavy pot over medium heat. Meanwhile, finely chop carrot, celery, onion, and parsley.
When the oil is hot, add the chopped vegetables to the pot together with a whole garlic clove, lightly crushed, along with sage, rosemary, and bay leaf. Sauté gently until the onion becomes golden and soft. In the meantime, finely mince the chicken giblets (optional; not everyone uses them) until they are very fine.
Add the ground beef and pork, the sausage (removed from its casing), and the optional minced giblets to the pot. Stir well and sauté until the meat has released all its moisture and has taken on a deep brown color, which should take approximately 30 minutes.
Once the meat is properly browned and dry, deglaze the pan with red wine and allow the alcohol to fully evaporate.
Add the passata di pomodoro and a spoonful of concentrato di pomodoro, stirring thoroughly.
Reduce the heat to low and let the sauce simmer gently for about 2–3 hours, stirring occasionally. If the ragù becomes too dry during cooking, add a small amount of broth as needed to maintain the right consistency.
Finally, remove the garlic, rosemary, sage and bay leaf from the sauce. Serve the ragù hot, traditionally paired with pasta.