Hold the artichoke head in one hand, snap off the stem and remove any tough fibres. Trim any spiky tops on the leaves with scissors. Using a stainless steel knife, cut away the top one-third of the globe.
Snap off the tough outer leaves until you reach the paler, tender ones. If you want to serve the artichoke whole and sitting flat, trim around the base of the artichoke; otherwise, trim the stems to about 4cm (1Β½inches) long and lightly peel them. Rub the cut surfaces with half a lemon to stop them turning brown. If the artichokes are to be served halved or quartered, slice them now and cut away the hairy choke with a knife.
If you arenβt using the artichokes immediately, prepare a bowl of acidulated water by squeezing the juice from 1 lemon into a large glass bowl of cold water. As you finish preparing each artichoke, drop it into the acidulated water and put a plate on top to keep it submerged. Set aside for 10 minutes.