Break off the stems, tear off the hard outer leaves—usually 10 to 15—until arriving at those paler in color and tender at the base. Slice off the top half of the remaining leaves, slice off the broken stem end, leaving the base flat, and force the leaves outward, one at a time, working circularly toward the center until the artichoke resembles an opened-out old-fashioned rose. Put the prepared artichokes into a large mixing bowl and pour over the olive oil, turning them around so that all surfaces are covered.
Soak the bread slices for a few seconds in hot water—only until they have swelled and the crusts are completely soggy; squeeze them out in your hands and mix them with the parsley, garlic, salt, and pepper, mashing and stirring with a fork, adding a tablespoonful or so of olive oil while working to render the mixture less resistant. Hold each artichoke upside down for a moment to drain it of excess oil, sprinkle the interior with salt, and place a heaping tablespoonful of stuffing on top, forcing it into the crevices and smoothing the surface with the palm of your hand. Arrange them in a gratin dish just large enough to hold them without having to force them into place (enough space should be left to permit basting). Pour the oil that was drained from them over the stuffed surfaces—about