Aquafaba

Aquafaba (/ˌɑːkwəfɑːbə/) is the name for the viscous water in which legume seeds such as chickpeas have been cooked.

Due to its ability to mimic functional properties of egg whites in cooking, aquafaba can be used as a direct replacement for them in some cases, including meringues and marshmallows. Its composition makes it especially suitable for use by people with dietary, ethical, or religious reasons to avoid eggs.

The most common use of aquafaba is as a replacement for egg white. It is composed of carbohydrates, proteins, and other soluble plant solids which have migrated from the seeds to the water during the cooking process. This unique combination of ingredients gives it a wide spectrum of emulsifying, foaming, binding, gelatinizing and thickening properties.

The general recommendation for use is to replace one medium egg white with 30 millilitres (2 tablespoons) of aquafaba in a recipe, or to replace one medium whole egg with 45 mL (3 tbsp)

The simplest way to use it is to decant the liquid from canned or boxed legumes such as white beans or chickpeas. Alternatively, it can be made by boiling, steaming, pressure cooking, or microwaving pulses in water until they are cooked.

Sweet applications where a direct substitution for egg whites has been found to be successful include meringues, macarons, nougat, icing, ice cream, fudge, and marshmallows.

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Wikipedia