Open a can of chickpeas and drain the water out of the can and into the bowl of your electric mixer. It should be around ¾ cups (180ml). Add in the cream of tartar.
Start mixing at low speed and let the mix become foamy before you gradually increase the speed until you're mixing at high speed.
Let the mixer run until your chickpea brine and cream of tartar mix has reached the stiff peak stage. This can take varying amounts of time from a few minutes up to 10 minutes or more.
Add the powdered sugar and whisk again until well mixed and there are stiff peaks again.
Now melt your chocolate by breaking it up into pieces and placing it into a microwave safe bowl. Microwave in 30-second increments, bringing it out to stir every 30-seconds until it's melted.
Add the peppermint extract to the chocolate and mix in.
Let the chocolate cool a little before folding the melted chocolate into the whipped aquafaba mix being careful to incorporate it slowly, folding it in gently.
You will notice that the aquafaba mix collapses a little once the chocolate is mixed in, don't worry about this, it's fine. As long as you fold the chocolate in and don't mix too much, it will still be fine.
Pour equal amounts of the mousse into serving glasses and place them into the coldest part of your refrigerator to set for an hour or two.
Serve with vegan whipped cream and vegan chocolate shavings (optional).