In a small sauce pan, combine orange juice and honey. In a small bowl combine cornstarch with 1 tablespoon of water. Stir in orange juice-honey mixture. Cook over medium heat until thickened and bubbly, stirring constantly. Add butter and cooked peel. Continue to cook until butter melts, stirring constantly. Slice roast, garnish with reserved orange sections and sliced mango. Serve with sauce and spinach salad.