"All sorts of impossible things can be done when nothing else matters any longer," he says grimly.
"Another time, perhaps," he grimaces. "I can about manage toast at the moment." He takes out his wand. "Let's observe your results. By time and thickness first, vertical and horizontal axes respectively--" A swishflick and a few muttered words spread the cabbage bits into a square on the table, showing when Q was cutting thinner and when thicker. "And now, by time and evenness." Another little spell, and when Q has gotten a good look at the new chart, he returns the cabbage to its uncut state, bisects it again. "Pick up the knife."