Add a slow cooker liner to crockpot.
In a skillet, heat oil.
Dice onion and bell pepper.
Add to hot oil.
Saute for 4-5 minutes, or longer until onions are translucent and softened.
Scoop into the bottom of the slow cooker.
In same pan, cook meat, unless using sausage crumbles.
Once the meat is browned, add to the slow cooker.
Into Slow Cooker, add tomatoes, sauce, paste, chicken broth, and seasonings.
Cook on low for 6-8 hours. Longer means deeper flavor.
30 minutes before serving, add spinach, zucchini, and mushrooms if using.
20 minutes before serving, cook pasta*.
Serve - ½ cup cooked pasta in the bottom, 1 spoonful cheese, ladle over soup, sprinkle with mozzarella