Butterflying a single boneless skinless chicken breast is a great way to speed up its cooking time. This thin cut is also called a paillard or a scallopine and is perfect for grilling or sauteing.
 

Place the breast on the board skin-side down. Remove the tenderloin. Most of the time you can just pull it off, but you might need to cut it free at one end.
 

Turn the breast over with the tip facing you and the thinner side opposite your cutting hand.
 

Place your hand on top of the breast. Carefully insert the knife into the thickest part of the breast, and draw it almost all the way through the breast. Take care to keep the breast attached on one side.

 

Open the breast like a book and, if needed, use the broad side of a cook's knife to even out the butterflied breast, by lightly pounding the flesh until it's an even thickness.