In a stand mixer fitted with the whisk attachment, or using an electric hand mixer, whisk chickpea liquid for two minutes on high speed.
Mix in powdered sugar a little bit at time.
Mix in cream of tartar.
Keep mixing until stiff peaks form. This takes around 10 minutes.
Mix in vanilla bean paste.
Pipe on cupcakes.
If desired, use a culinary torch to create a toasted look.
Serve immediately.
Notes
This frosting lasts about 20 minutes on the counter or about two hours in the refrigerator before collapsing. If you aren't planning to serve the meringue immediately, place the bowl of meringue in the refrigerator and, when ready to eat, whisk to redevelop the peaks before piping and serving.