To the insert of a slow cooker, add tomatoes, tomato sauce, tomato paste, onion, garlic, basil, salt, pepper, and chicken broth. Whisk or stir to combine.

Cover and cook on LOW for 6-8 hours, or HIGH for 3-4 hours.

About 40 minutes before you want to serve the soup, use an immersion blender, or transfer soup (in batches) to a traditional blender and blend until smooth. If using a traditional blender, transfer soup back to the slow cooker after blending.

In a small saucepan over MED heat, add butter. Once melted, whisk in flour. Cook for 1 minute, whisking often. Slowly whisk in the heavy cream and evaporated milk and cook a few minutes, whisking often, or until smooth and thickened slightly. Stir in parmesan cheese until melted.

Transfer heavy cream mixture to slow cooker with soup and give a good stir to combine.

Don't cover, and cook on HIGH for about 20 minutes or so, until thickened a little bit, and well combined.

Serve hot, garnished with additional grated Parmesan cheese and minced fresh basil if desired.