Heat the oil in a saucepan, add the chicken and onion and fry, breaking up the mince with a wooden spoon until browned. Mix in the garlic, paprika, chilli and cumin seeds and cook for 1 minute.
Stir in the tomatoes, beans, stock and sugar, then mix in the chocolate and seasoning. Cover and simmer gently for 45 minutes, stirring occasionally. Spoon the chilli into bowls to serve