In a large sturdy pot, heat olive oil over medium heat.
Add celery, carrots, onion and saute about 10 minutes. Do not brown onion.
Add garlic to pot. Saute 1 - 2 minutes to release flavor.
Add ground beef, pork/Italian sausage to pot. Breaking up meat into small pieces. Cook about 10 minutes until meat is no longer pink.
Add chicken stock, crushed tomatoes, tomato puree, tomato paste, sage, salt and pepper.
Bring to boil and then turn heat down to a slow simmer. Simmer for about 2 hours with lid ajar.
If sauce gets too thick, add some extra chicken stock.