aquafaba
How to use Aquafaba as an egg substitute?
Aquafaba is the liquid from cooking legumes, like the liquid from canned chickpeas/garbanzo beans, or liquid from beans cooked at home. Since that liquid has a very similar consistency to that of raw egg white, it works as an excellent substitute in recipes which uses egg whites like macaroons, meringues, marshmallow, nougat, cakes, etc.
3 tablespoons aquafaba can be used to replace one egg/egg white.
The only thing to note is that the consistency should be right. It can't be too thick or too watery.
Aquafaba can be used straight from the can, by draining the chickpeas or any legume. Chickpeas, white beans are preferable because the aquafaba will be clear and transparent. You may choose to use the liquid from red kidney beans and black beans in chocolate cakes or brownie recipes.
If the liquid is thin, heat it up until it reduces and gets a bit thicker. If it gets too thick, heat it up with some water to make it thin. Either way, cool it to room temperature before use.