Put all ingredients in a large Crock Pot or slow cooker
Cook on low for 6-8 hours
When finely chopped veggies are very soft and cooked through the soup is done
Finish soup with an immersion blender or put in small batches in the regular blender
Garnish with additional basil and parmesan
You can make the soup creamier by adding sour cream or plain Greek yogurt at the end as a garnish or blend in well with entire batch. This makes a big batch and freezes well.
Allow the soup to cool before ladling it into freezer-safe containers or freezer bags, just make sure you don't add any dairy before freezing it. Soup can be frozen for 4-6 months, and then thawed overnight in the refrigerator.
If you don't have an immersion blender a regular blender will work well too. Just blend in batches and be careful with the hot liquid.