Chef John's Lemon Bars
This is one of my favorite cookies of all time, although technically they're closer to a pie than a cookie. Nothing prepares you for that intense, awesome sweet-tart lemon flavor and custard, perfectly contrasted against that crisp, sweet buttery shortbread cookie.
To add a meringue topping, whisk 1 egg white in a bowl until it forms a ribbon, add 1 tablespoon of white sugar, and whisk until mixture holds soft peaks. Spoon meringue into a resealable plastic bag, cut a corner off the bag, and squeeze meringue on top of cut bars in a decorative pattern. Brown meringue lightly with a kitchen torch.