2) In a medium saucepan melt the butter and saute the onions and jalapeno, until tender. Season with cayenne, and salt and pepper. Add the ginger, brown sugar, orange juice and tomato ketchup in that order, making sure to blend each ingredient completely before adding the next ingredient.
3) Allow to simmer until the edges begin to caramelise, about 15 minutes. Set aside and leave to cool. Once cool, remove half the sauce and reserve for dipping. The other half is for brushing on the prawn whilst griddling.
4) Cut the bacon in thirds. Thread each prawn onto a skewer, starting from the tail end. Bend the prawn as you thread it so it lies in a straight line on the skewer, removing its natural curve.
5) Wrap the centre of each prawn with a piece of bacon. Brush with sauce and place the skewers with bacon, seam side down, onto the griddle.
6) Cook over a medium heat until the bacon crisps and the prawn is cooked through, about 8 minutes.