Take your time whipping the egg white into the butter and sugar mixture! Because we’re using such small quantities of everything in this recipe, it’s especially important to thoroughly combine the egg white with the butter mixture. We recommend using a hand mixer here to keep things easy, but you can also use a whisk and some elbow grease (if you use a whisk, we recommend beating the butter, vanilla, sugar, and egg white together all at once, instead of first creaming the butter and sugar together. It’s easier to whisk by hand when you have the extra moisture from the egg white!) You want to beat the egg white and butter mixture together until the mixture is smooth, fluffy, and no longer grainy or separated. This will give you the smoothest cookie with the best texture! 

Equipment notes. We recommend using a hand mixer to cream the butter and sugar, and again to whip the egg white into the butter mixture. Once the egg white is properly mixed, switch to a plain spoon or spatula to fold in the remaining dry ingredients. We use a 2-3 Tablespoon cookie scoop to portion out the cookie dough, which yields about 6 cookies. Feel free to use a different size cookie scoop if you like (just remember to adjust the baking time for larger or smaller cookie sizes). 

Please use a kitchen scale! Measuring ingredients by volume (with cups) is notoriously unreliable: For best results, use a kitchen scale and measure your ingredients by weight using the gram measurements above. If you don’t have a scale, measure your flour with the scoop-and-level method for best results. We recommend this kitchen scale. 

Additions and Substitutions. Use white chocolate chips or chopped baking chocolate in place of the chocolate chips. Add a small handful of nuts, dried cranberries, or extra chocolate if you like. Swap the butter for coconut oil in its solid, room-temperature state (if you use coconut oil, be sure to chill the cookie dough for half an hour before baking for the best texture).

For prettier cookies, press a few extra chocolate chips into each cookie dough ball just before baking. The chips will stay on the surface of the cookies so you can see plenty of chocolate even after baking!

Optional: Chill the cookie dough. Mix the dough as directed, then pop it in the fridge (uncovered is fine) for 30 minutes before scooping and baking the cookies. This quick chill lets the butter set a bit so that it melts more slowly in the oven, giving you a chewier cookie with lighter color. 

Store cooled cookies in an airtight container on the counter for up to 4 days, or freeze for up to 4 months.