Cut and peel white membrane from one orange cut into slices, then into half-cartwheels. Set aside for garnish. Grate peel from part of 1 orange to make 1 teaspoon. Set aside. Ream juice from orange with grated peel and remaining orange to make approximately 3/4 cup juice. In large skillet, heat butter and oil over medium heat. Add chicken and brown on all sides. Add onion, garlic, chili and cumin. Pour over orange juice, peel and agave. Cover and simmer until chicken is tender (about 15 minutes), turning pieces once. Remove chicken to serving plate or place on bed of cooked rice. Mix cornstarch into yogurt. Stir into pan juices and cook just until thickened. Season to taste with salt and pepper. Pour sauce over chicken and garnish with orange slices and parsley.