What should I do about the very crumbly cookie dough from Food52's Erin McDowell's recipe?

Next time try kneading the cookie dough just a bit. Sometimes that works with crumbly cookie dough in combination with a touch of liquid.

I recently made Dorie Greenspan's world peace cookies, and the dough was really crumbly. I (gently) worked in about a tablespoon of room temperature butter, and that kept the dough together and the cookies came out fine.

I'm not sure which of Erin's recipes you're referring to, but with crumbly doughs I tend to add a teaspoon or two of milk to dampen the dough and get it to stick together. I hope this is helpful!