In a large, high-sided bowl, combine the bean liquid, cream of tartar, vanilla extract, and a heaping tablespoon of the sugar, and whip with an electric hand mixer on high, adding sugar by the heaping tablespoon until it's all incorporated. Continue whipping until your aquafaba forms soft peaks. This can take anywhere from 15-25 minutes.
Scoop tablespoons of your meringue onto cookie sheets lined with parchment paper.
Bake each batch for two hours. Your cookies are ready when they’re crisp all the way through. If they look runny at all, give them 10 extra minutes, then check again.
Turn the oven off, but leave the meringues in there for another 2 hours to cool before removing from oven.
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Notes
Make sure that your bowl is squeaky clean before you start cooking. Any residual oil will interfere with you getting those good, stiff peaks.I do not recommend hand-mixing, unless if you’re up for an endurance workout. It took me 15-20 minutes to get nice, soft peaks. You’re not going to get a super dense, sticky texture, but the peaks should hold when you lift the whisk out of the bowl. If the mixture is runny, keep mixing.Store cooled meringue cookies in an airtight container on the kitchen counter or in the pantry. They will keep for two to three days. Your meringue cookies will soften over time, because they will absorb moisture from the air. How long they keep depends a lot on how humid your kitchen is.