Remove any excess fat pieces from the cavity of the duck. Remove the neck flap. With the duck breast side up and the cavity facing you, make a 1 inch slit on each side of the breastbone inside the cavity. Insert 1 slice of the jalapeno and 1 clove of garlic in each hole. With your fingers, separate the skin from the breast meat and insert 5 pieces of jalapeno and 5 garlic cloves under the skin and push them well along the breast. Turn the duck around so that the neck is facing you. Slice the remaining 2 cloves garlic and put these and the remaining jalapeno slices in the neck cavity. Put the duck in a deep glass or plastic container. Squeeze the lemons and pour the juice over the duck and inside the cavity. Rub the duck with the lemon skins. In a small bowl, stir the sugar with salt, pepper, and cayenne. Rub the duck, inside and out, with this mixture. Cover and refrigerate for 8 hours. Preheat the oven to 450 degrees F. Remove the duck from the container and place it on a rack in a roasting pan. Stuff the cavity with the sweet potatoes and head of garlic. Bake for 30 minutes. Reduce the heat to 350 degrees F. and continue to bake for 1 hour, or until the duck legs pull easily away from the body. Carve the duck into 4 pieces. Peel and chop the sweet potatoes. Squeeze the garlic from the skin and set aside. Pour the oil (about 1/2 cup) from the roasting pan into a large skillet and heat over medium-high heat for about 2 minutes. Add 1 tablespoon flour and blend with a wire whisk for 5 to 6 minutes to make a medium brown roux, the color of peanut butter. Add 1 cup each chopped onions and celery and cook stirring often, for 5 to 6 minutes. Add the chopped sweet potatoes and roasted garlic. Cook, stirring occasionally, for about 3 minutes. Add the chicken stock and bring to a boil. Reduce the heat to medium-low and cook, stirring occasionally, until the mixture thickens 6 to 7 minutes. Season with salt, cayenne and the Steen's Cane Syrup. Simmer for about 3 minutes. Add the green onions and parsley. Lay the duck pieces in the sauce and spoon it over. Increase the heat to medium, cover, and cook for about 20 minutes. Remove the lid and cook for 5 minutes more. To serve, place a piece of duck in the center of each plate and spoon the sauce over the top.