1. Combine first 7 ingredients in a large bowl. Add chicken, turning to coat.
2. Heat oil and butter in a tagine or Dutch oven over medium heat. Add chicken, skin side down, and cook 4 to 5 minutes per side or until golden brown. (Cook in batches, if necessary.) Transfer to a plate.
3. Add garlic to pan, and sauté about 1 minute. Add mint, thyme, broth, chicken, and any juices that drained onto plate. Cover, reduce heat to low, and simmer 30 to 35 minutes or until chicken is tender.
4. Bring onion and next 3 ingredients to a simmer in a separate saucepan over low heat; cook 8 to 10 minutes or until lemon becomes soft and liquid thickens. Discard herb sprigs; pour glaze over chicken, and garnish, if desired.