Swordfish

Ironman verdict

At least 8 monsters drop it. The easiest is Mighty banshee (level 61, 12/128); the best rate is Chaos Elemental (level 305), at 18/129, about 1.4 per kill. You can also make it yourself: it takes 45 Cooking and gives 140 Cooking XP, using Raw swordfish. There is one other recipe below. Other sources include Gourmet impling, Gourmet impling jar, Managing Miscellania and Hamper, plus 2 more listed below. Making ten takes 10 × Raw swordfish and gives 1,400 Cooking XP. Reaching level 45 Cooking takes 61,512 XP in total; the Cooking calculator counts the actions and materials to any target, and the Cooking guide has the Ironman training route. 5 recipes use Swordfish, including Attuned portent of restoration VI, Calorie bomb (swordfish) and Cooking potion (3). Swordfish is available on free-to-play worlds too. It is tradeable on normal accounts, but an Ironman cannot use the Grand Exchange or trade for it, so the sources on this page are the whole list. High Alchemy turns one into 240 coins, which is 160 less than the shop price, so buying it to alch does not pay.