The Witches' Brew

The full recipe is:

First Witch
Round about the cauldron go; In the poison'd entrails throw. Toad, that under cold stone Days and nights has thirty-one Swelter'd venom sleeping got, Boil thou first i' the charmed pot.

All
Double, double, toil and trouble; Fire burn, and cauldron bubble.

Second Witch
Fillet of a fenny snake, In the cauldron boil and bake; Eye of newt and toe of frog, Wool of bat and tongue of dog, Adder's fork and blind–worm's sting, Lizard's leg and howlet's wing, For a charm of powerful trouble, Like a hell–;broth boil and bubble.

All
Double, double, toil and trouble; Fire burn and cauldron bubble.

Third Witch
Scale of dragon, tooth of wolf, Witches' mummy, maw and gulf Of the ravin'd salt–sea shark, Root of hemlock digg'd i' the dark, Liver of blaspheming Jew, Gall of goat, and slips of yew Sliver'd in the moon's eclipse, Nose of Turk and Tartar's lips, Finger of birth–strangled babe Ditch–deliver'd by a drab, Make the gruel thick and slab: Add thereto a tiger's chaudron, For the ingredients of our cauldron.

All
Double, double, toil and trouble; Fire burn and cauldron bubble.

Second Witch
Cool it with a baboon's blood, Then the charm is firm and good.

Notes:

Toad, that under cold stone ...	The toad is only ready for the pot after a month spent under a stone synthesising its poison
Fenny snake	A snake that lives in the Fens of East Anglia
Blind-worm	Another name for the slow-worm, which is not actually blind but is noted for its small eyes. As far as I know it doesn't sting either
Howlet	An owlet, i.e. a baby owl
Witches' mummy	The flesh of a mummified body - this was apparently used as a medicine both long before and long after Shakespeare's time
Maw and gulf	Stomach and throat
Ravin'd	Ravenous
Sliver'd	Sliced
Nose of Turk ... birth-strangled babe	A baby that's killed immediately after birth and before baptism is condemned to damnation, like the unbaptised Turk, Tartar and Jew
Drab	Prostitute
Slab	Glutinous
Chaudron	Entrails