I got this from http://sisterscafe.blogspot.com/ and LOVED it. We all did. Enjoy!
2 (14oz) cans diced tomatoes, with juice 1 cup finely diced celery 1 cup finely diced carrots 4 cups chicken broth 1 cup finely diced onions 1/2 bay leaf 1 tsp dried oregano or 1 Tbsp fresh oregano 1 Tbsp dried basil or 1/4 cup fresh basil 1/2 cup butter 1/2 cup flour 1 cup Parmesan cheese 2 cups half and half, warmed 1 tsp salt 1/2 tsp black pepper
In a large slow cooker, combine tomatoes, celery, carrots, chicken broth, onions, bay leaf, oregano, and basil (if using fresh oregano and basil; if using dried oregano and basil add those two ingredients in the last hour of cook time). Cover and cook on low for 5 to 7 hours, until flavors are blended and vegetables are soft.
About an hour before serving prepare a roux: Melt butter over low heat in a skillet and add flour; stir constantly with a whisk for 5 to 7 minutes. Slowly stir in 1 cup hot soup from the slow cooker. Add another 3 cups soup and stir until smooth.
Add all back into the slow cooker. Stir and add Parmesan cheese, warmed half and half, salt and pepper. Cover and cook on low for another hour until ready to serve. Garnish with Parmesan cheese and freshly ground black pepper to taste.