Add boneless skinless chicken breasts, diced tomatoes (14 oz), tomato sauce (8 oz), minced garlic, Italian seasoning, salt, and black pepper to the crock pot.
Cover and cook on low for 4–6 hours or on high for 3 hours.
In a small mixing bowl, whisk together heavy cream and corn starch until smooth.
Stir the heavy cream mixture into the crock pot during the last 30 minutes of cook time.
Stir in fresh basil finely chopped before serving.