To butterfly a piece of food is to split it along its length, separating it into two halves that remain joined along one edge like a book. The technique is applied to meat, poultry breasts, fish fillets, and shell-on prawns, producing a thinner, larger piece that cooks quickly and evenly. Opening out the flesh also creates a pocket for stuffing with herbs, cheese, or other fillings. Even thickness is the goal: the opened piece should lie flat so heat reaches all parts at the same rate. Butterflying is a staple of grilling and barbecue preparation, where thin, uniform pieces sear beautifully over high heat.