In a large slow cooker, combine the chicken broth, tomatoes, celery, carrots, onion, 2 tablespoons of the basil, bay leaf, and oregano. Stir to combine. Place the cover on the slow cooker and cook on low for 5-7 hours, or until the vegetables are soft.
An hour before you are ready to serve, transfer half of the soup to a blender or a food processor and process until smooth. Return the mixture to the slow cooker.
In a saucepan, melt the butter. Whisk in the flour and cook for a minute. Slowly whisk in about 1 cup of the soup from the slow cooker. Add an additional 3 cups of soup and stir until smooth. Mix back into the slow cooker.
Stir in the Parmesan cheese, warmed half and half, and the remaining basil. Season to taste with salt and pepper. Cook on low for an additional hour.
Notes
adapted from Recipe ShoeboxSUBSTITUTIONS: You can use vegetable broth to make this soup vegetarian, but I love the flavor that the chicken broth brings. If you don’t have half and half, part milk and part cream will work. Or use a combination of evaporated milk and regular milk.FREEZE: I would not suggest freezing this soup. Because of the dairy in the soup. The texture will become grainy.STORE: Store any leftovers in the refrigerator for 3-5 days.Nutrition information provided as an estimate only. Various brands and products can change the counts. Any nutritional information should be used as a general guide.