Wash and lightly scrub the potatoes with a vegetable brush and dry thoroughly with kitchen paper. Prick all over with a sharp knife. Put the potatoes in the microwave on a microwave-safe plate and cook for 5 mins. Turn the potatoes over and cook for another 5 mins, then set aside covered with a tea towel.

Put the prawns, dill, a squeeze of lemon juice and the mayonnaise in a bowl and stir gently to combine. Taste and season with pepper to taste. Cut open the warm potatoes. Divide the butter between the potatoes, then pile the prawn salad on top. Serve with a sprinkling of dill and a lemon wedge on the side.