This method is extremely click intensive, but offers the best XP rate that you can get for cooking and even nets a small profit. Karambwans will not stop burning until level 99 with a Cooking Cape, 94 at the Hosidius Kitchen or 93 at the Hosidius Kitchen with Cooking Gauntlets.
Hold down the 2 key and use one Karambwan on the fire/range every tick. The best places to do this are the Myth’s Guild range or the inferno bank because people can’t stand on top of the fire. Otherwise, you can use Rogue’s Den as well.