Mix and chop together the onions, garlic, parsley, salt, pepper, and soaked bread. Spread a bit more than half of the mixture in the bottom of a generously oiled gratin dish. Pour ½ cup of olive oil into a bowl, pare the artichokes to hearts, split each in two, remove choke, if necessary, and slice each half, in the sense of the leaves’ length, into ¼-inch thicknesses, plunging the slices immediately into the olive oil and turning them around in it to coat them thoroughly. When all are finished, turn the mass well together with your hands and turn it out onto the layer of bread mixture, spreading it evenly over the surface and pressing it firmly into place. Spread the remaining bread mixture on top, pressing with the palm of your hand to create an even, smooth surface, sprinkle with cheese, dribble the remaining olive oil in a fine crisscross pattern over the surface, and bake in a hot oven (about 425°), turning it down to about 375° after 10 minutes or so. Count 1 hour to about 1 hour and 10 minutes; the surface, sides, and bottom should form a richly golden-brown, crisp encasement, easily detached from the dish and, within, the layer of artichoke slices should be of a white tenderness in their voluptuous and alliaceous sheath. Serve the lemon wedges apart.