Combine butter and Leggo’s Pesto in a small bowl.
Using a small sharp knife and cutting from back of the head to the tail, make a deep slit down through the back of a prawn, leaving tail intact. Discard vein. Repeat with remaining prawns.
Lightly brush a preheated BBQ grill plate with oil and press prawns “legs” side down. Cook for 1-2 minutes or until shells are lightly browned and prawns have changed colour. Turn over pressing lightly to open out shell. Continue to cook for a further 1-2 minutes.
Spread cut side of each prawn with pesto flavoured butter and serve immediately with lemon wedges.