How to butterfly a chicken breast
Butterflying is a cutting technique used by butchers to transform a thick, compact piece of meat into a thinner, larger one. The piece of meat to be cut is laid out flat on a cutting board and cut in half parallel to the board from one side almost all the way to the other. A small "hinge" is left at the one side, which is used to fold the meat out like a book. The resemblance of this unfolding motion to the wings of a butterfly is what gives this cut its name. This technique is often used as an alternative to, or in conjunction with, pounding out the meat with a meat mallet to make it thinner.
The same term is sometimes used for a technique, also called "spatchcocking", in which a bird is prepared for grilling or roasting by removing the backbone and sternum and then pressing down to fan it out.
Butterflying a lobster tail involves cutting the hard top side, without cutting all the way down to the other softer side.
Cover with greaseproof paper and hammer flat