Add oil and butter to a large saucepan over medium heat. Once melted, add the onion and cook, stirring occasionally, 5 minutes.
Add the garlic. Stir in the flour and cook for another minute.
Add the vegetable broth, diced tomatoes, tomato sauce, Italian seasoning, and dried basil. Season with salt and pepper. Taste broth and adjust seasonings if needed.
Bring mixture to a gentle boil and then add the tortellini. Cook for a few minutes, until tortellini are tender.
Remove from heat and stir in spinach, parmesan cheese, and cream.
Add chopped basil. Serve warm.