In a high-powered blender or food processor, blitz together the unsalted butter, grated ginger, garlic, coriander, lime zest and Maldon salt. Mix this until you have a smooth and vibrantly green butter.
Heat up the BBQ or alternatively you can you a griddle pan. Brush the prawns all over with the green butter until they are well coated. Place them on the griddle and cook for 2 minutes on each side until they are bright pink and cooked with light charring on their shells. Remove the prawns from the griddle and brush with some more of the butter, allowing it to soak in. Add the lime wedges to the hot griddle pan and cook them for a minute on each side to char.
Remove the lime wedges and squeeze them over the prawns. Sprinkle over the finely diced chilli and coriander leaves and the prawns are ready to serve.
