The adjustments I decided to make to this recipe are the replacement of egg whites with aquafaba, using sugar as the stabilizing ingredient. Aquafaba is the water in which beans have been cooked and it is often used as a plant-based egg white replacement because the proteins and starches in aquafaba resemble those of egg whites. To learn more about plant-based alternatives and how to apply them, click here.
By adding sugar, the aquafaba is able to form stiff, sticky peaks and the foam deflates less rapidly. The sugar also helps stabilize the foam “by increasing the viscosity of the water in the foam, slowing how quickly it can drain out” and allows the aquafaba to better hold its form when being folded into the coconut, condensed milk, and vanilla extract mixture. Since the sugar adds an obvious sweetness to the cookie, the amount of sweetened condensed milk should be reduced. This will alter the texture of the cookie a bit, making it less dense and chewy. It also will also have less of a caramelized flavor because the sugar will have dissolved in the egg whites and will not go through the same process of caramelization.
To understand more about aquafaba, click here.