Write your own parody of the "Double, double, toil and trouble" chant.

When one writes a parody, one is attempting to produce a funny imitation of an author or genre. It is often amusingly hyperbolic, or exaggerated. An audience has to be able to recognize the original text being parodied in order to understand both the similarities and the humor produced.
To begin your parody of this scene, you might want to come up with a scenario in which three women are working on something together. I think that having three females is crucial to ensuring that the original text of the parody is recognizable to your audience. You could choose some kind of stereotypical scenario, such as three mothers wishing that their children would clean up after themselves or that they would listen more, or three wives complaining that their spouses don't do enough around the house. These women could be casting a spell to make their children or spouses listen more or do more. Or you could choose something a bit less expected, like three women chanting about their political concerns or about the challenges of being queer in today's society.
It is also important to retain the way the sisters speak—in rhyming couplets—in order to make the original text clear. Their speech pattern is one of the most obvious stylistic choices that Shakespeare makes for their characters, and this is why it will be important to maintain. In addition to the end rhyme, the witches also speak in a meter called trochaic tetrameter. This means that there are four (tetra-) feet per line, each foot containing two syllables: an accented syllable followed by an unaccented syllable.

Dou ble | Dou ble | toil and | trou ble
Fi re | burn and | caul dron | bub ble

Each of the syllables in bold is accented, and feet are separated by "|." If you can manage to duplicate this meter, I'm sure your teacher would be thrilled! However, if you haven't studied meter, then I think you could probably get away with simply duplicating the end rhyme.
This is a really cool assignment. Good luck!