Press a chile against a work surface and cut a line along its length, stopping just short of the stalk. Rotate the chile by an eighth of a turn and cut again. Repeat this until you have 8 cuts and the chile looks like a tassel when you hold it by the stalk. Now hold the chile down firmly with three fingers, the middle one slightly in front of the others, and, using the knuckle of your middle finger to guide the blade, slice across the chile, gradually working your way toward the stalk.