Mix the marinade ingredients (tamarind pulp through oil), add chicken and set aside to marinade for at least 20 minutes.
To prepare the peanut sauce heat the oil in a saucepan add chillies and garlic and cook over medium heat until soft (about 5 minutes). put the mixture into the food processor and add the peanuts, salt and sugar. Process briefly so that the peanuts are still chunky. Add hot water and process again to make a thick sauce.
Thread 4 chicken cubes onto each skewer. Grill on the barbecue or griddle pan until golden brown on both sides and cooked inside. Serve with dipping bowls of peanut sauce rice or pita bread and fresh cucumber salad.