Fennel and Tomato Soup

In the large pot, heat the oil over medium-high heat and add the fennel, onion, and potato. Reduce the heat to medium low and let the vegetables sweat for 10 minutes, taking care to not let them brown. Add the tomatoes and cook for 10 minutes more. Stir in the chicken stock; bring the mixture to a boil. Reduce to a simmer and cook for 1 hour.