Trim off the
sharp points (if any) at the ends of the artichoke leaves, then put the
artichokes with the vinegar into the water. Bring to the boil and boil
gently for about 30 minutes. When cooked, the bottom leaf should come
away easily if pulled gently. Remove the feathery 'choke' with a spoon
and discard. Leave the artichokes upside down to drain and cool. Serve
with the vinaigrette dressing.