In a stockpot, brown lamb in 2 tablespoons oil. Remove and set aside.
In the same pan, saute onions and peppers in remaining oil until tender. Add garlic; cook 1 minute longer. Add the beans, tomatoes, broth, oregano, chili powder, brown sugar, Worcestershire sauce, cumin and fennel. Return lamb to the pan.
Bring to a boil. Reduce heat; cover and simmer for 1-1/2 to 2 hours or until lamb is tender. Garnish servings with onions, tomatoes and corn chips if desired.
Serve immediately or cool and freeze in a freezer container for up to 3 months. To use frozen chili: Thaw in the refrigerator. Transfer to a large saucepan; heat through, adding water to thin if desired. Garnish each serving with green onions, tomatoes and corn chips if desired.