Clean the artichokes: remove small leaves from the bottom, cut away a third down from the top, clip point of remaining leaves, remove stem flush (clean stem and add to cooking). Try to remove choke (very hard)
Put artichokes in pressure cooker top down with half an inch of water. Add vinegar/lemon to the water.
Cook in pressure cooker for 10 minutes from the beginning of the hissing.
For the sauce:
Thin the mayonnaise with the olive oil and the lemon juice. After the artichokes are cooked, add some of the cooking water.
Dish the artichokes, gently part them open (try to remove the choke) and pour the sauce in the middle