In thunder, lightning, or in rain.

When the hurly-burly’s done,

When the battle’s lost and won.

   
What the boys need is a cauldron…

 Not quite black iron but it’ll do! The advantage is it’s already full and not of Eye of newt, or toe of frog, Wool of bat, or tongue of dog, Adder’s fork, or blind-worm’s sting, Lizard’s leg, or howlet’s wing.