First, using the flat of your vorpal blade, smash the TumTums into a tulgey paste. Put them over a galumphing flame for 5 minutes. If you hear them snicker-snack, you have the flame too high, remove and wait for the manxome bubbles to subside.
While you are waiting for your TumTums to whiffle, carefully quarter you bundersnatch and prepare it for roasting.
Mince your toves (pick out any slithy ones) and borogoves (if in season, opt for the mimsiest ones you can find). Mix together and apply as a dry rub to the skin of the Bundernatch