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.