Cut the sweet potatoes into small cubes. Make small slits in the chicken pieces.
To make the marinade mix hoisin sauce, sugar, salt and pepper powder in a bowl. Put the chicken pieces, mix and set aside to marinate for 2 hours.
Heat 2 tbsps oil in one non stick pan and 1 tbsp oil in another non stick pan. Add sweet potatoes to one pan and sauté till crisp. Chop jalapeno.
Put the chicken pieces, skin side down, on the other pan, drizzle some of the extra marinade over and cook.
Chop fresh red chilli. Add jalapeno and red chilli to sweet potatoes. Add salt and squeeze the juice of ¼ lemon and mix.
Add a little water to the chicken, cover and cook. When the underside is done, turn them over, drizzle some more of the remaining marinade, a little water and cover. Cook till chicken is completely cooked.
Arrange the sweet potatoes in the centre of a serving plate, keep the chicken pieces on them, drizzle the sauce left in the pan over and serve hot.