Heat a medium soup pot over moderate heat. Add oil, shallots and garlic. Sauté 5 minutes. Add drained tomatoes and crushed tomatoes, stir. Add stock and stir to combine soup. Stir in spinach in handfuls to wilt it and combine with soup. Season soup with salt and pepper to your taste. Bring soup to a bubble, reduce heat and simmer 10 to 15 minutes to reduce.