Place chillies, and garlic in a frying pan over a medium heat and dry fry for around 6 minutes. Once cooled peel the garlic and deseed chillies (if you dont want it too hot). Place garlic and chillies into a blender along with the remaining ingredients for the piri piri sauce and blend until smooth.
Pre-soak Bamboo skewers for at least 30 minutes in water, this will prevent the skewers from burning on the BBQ. Preheat a BBQ or griddle to a medium-high heat. Remove heads and legs from the prawns (though Poppa Wan likes to leave these on) and carefully cut along the back of the prawns and remove the digestive track or vein (as some call it).
Place prawns into a bowl along with half of the piri piri sauce and mix ensuring each prawn has a liberal coating of the sauce. Thread 2-3 prawns onto each skewer and cook for around 3 minutes on each side.
Serve with the remaining piri piri sauce along with a wedge lemon.