Peel the onion and cut in half from root to stem. Place the half onion in front of you with the root end away from you. Slice the onion from side to side just short of the root end leaving it intact. Slice horizontally through the slices 3 times, again leaving the root intact. Slice the onion crosswise down through the other cuts. Onion will fall into pieces. With a rocking motion of your chef's knife continue to chop until fine.