Put homemade chicken stock into a large heavy soup pot and start to heat.
Add the dried basil, ground fennel, and 2 cans petite dice tomatoes with juice and let the mixture simmer while you cook the sausage.
Heat 1 T of olive oil in a heavy frying pan.
Squeeze the sausage out of casings and cook until nicely browned, breaking apart with a metal turner as the sausage cooks.
Add browned sausage to the soup pot.
Add the other 2 tsp. of olive oil to the frying pan, then cook the onions for 3-4 minutes, or until they are starting to soften.
Add the minced garlic and cook 1-2 minutes more.
Add the onion and garlic to the soup pot.
Deglaze the frying pan with about 1 cup of soup from the pot and scrape off browned bits from the pan, then add that back into the soup.
Let this simmer on low heat for 15-20 minutes.
Add the macaroni or frozen cauliflower rice, stir, and continue to simmer the soup for 15-20 minutes more, or until the macaroni or cauliflower rice is soft.
Stir in the basil pesto and cook 5 minutes more.
Serve hot, with freshly grated Parmesan cheese if desired.
