I didn't give up, though; I just took notes and kept on trying! I tried different ingredients, different protein powders, and different cooking approaches until I was able to separate what works from what doesn't.
To make a great batch of protein cookies, you need to remember three important things:
1. Make sure your mixture is no more than 1/8 protein powder, especially if you use whey. Otherwise, the whey will cook and your cookies will turn out rubbery and weirdly bread-like.
2. You need to have some fat in your batter. Egg yolk, nut butter, and coconut butter all work great.
3. Nuts and flaked coconut are a great way to add both crunch and flavor without adding sugar or carbs.
These guidelines aren't the "end all, be all" of protein cookie-making, but I think they represent three really important guidelines to remember.