Step 1

Butterfly the prawns, removing the black thread that runs through the body. Beat the butter until smooth, then mix in the harissa, parsley, capers, lemon zest and some ground black pepper. Can be made 2 weeks in advance, then chilled.

Step 2

Open out each prawn and smear 1 tsp of the butter into the middle. Can be made 1 day ahead and chilled.

Step 3

When ready to eat, heat the grill to as high as it will go. Put the prawns on a baking tray and grill for 5 mins until they are pink through. Toast the flatbreads, then serve with the hot prawns and lemon wedges for squeezing over.