Put the chillies in a small blender or food processor and process into a paste. Set aside.
Put the meat on a board and gently pound with a meat mallet to flatten.
Put the chilli paste, allspice, pepper, and pastes into a large shallow dish. Season with salt and mix well.
Add the meat and rub the marinade all over until coated. Cover and allow to marinate in the refrigerator for 4-5 hours.
Take a flat piece of rough granite, wash it and place it on 2 bricks making sure it is stable. Heat the granite well by placing live charcoals under it. Sprinkle a little oil on the granite and, working in batches, add the marinated meat pieces. Cook, turning a couple of times and brushing them lightly with oil, for about 4-5 minutes on each side. Remove with tongs and keep warm. Alternatively, cook the meat over a charcoal grill or on a griddle (ridged grill pan).
Serve with sliced onions, lemon wedges, mint leaves, and fresh mint chutney.