Trim artichoke stems, leaving about 1/2 inch, so that they will stand upright. Pull off the short, tough lower leaves of the artichokes. Cut off the top 1/2 inch of each artichoke, then use a scissors or sharp knife to trim off the sharp points of the remaining leaves. Rub the whole artichokes, especially the cut portions, with the cut side of the half lemon. Turn the artichokes upside down and rap them on a counter to loosen their leaves, then gently spread the leaves open like a flower. Spoon the breadcrumb filling into the openings, filling the leaves. Tap each artichoke lightly on the counter to help the filling settle inside the leaves.