These are adapted from Alison Roman’s Instagram-viral Salted Butter Chocolate Chunk Shortbread from Dining In, nipped and tucked. I used unsalted butter instead of salted, because it’s what I always have around. I reduced the butter and sugar creaming time, to yield a more classic, crumbly shortbread texture. For the same reason, I swapped out some of the flour for cornstarch, and increased the bake time. And, most notably, I turned the chocolate chunks into chocolate shards by chopping them much more finely. This not only makes slicing the logs noticeably easier, but turns the shortbread delightfully marbly and streaky. —Emma Laperruque
Chop the chocolate chips or chunks with a knife to yield fine shards—some of it will be chunky, some of it will be powdery.
Combine the butter, sugars, and salt in the bowl of a standing mixer fitted with the paddle attachment. Stir on medium-low, just to combine, 1 to 2 minutes. Scrape down, add the vanilla, and stir again. Add the flour and cornstarch and stir, medium-low, scraping as needed, until a dough just starts to form. Stir in the chocolate shards until just combined.
Dump the dough onto a clean work surface and divide in half. Form and roll each into a 6-inch long log and wrap in plastic film. Chill until firm—at least 1 1/2 hours, up to several days.
When you’re ready to bake, preheat the oven to 350° F. Brush the logs with the egg, then roll in the raw sugar. Using a serrated knife and sawing motion, slice the logs into 1/2-inch-thick cookies. Place on a baking sheet, 1 to 2 inches apart. Sprinkle with flaky salt. Bake for 16 to 20 minutes, until the sugary sides are deeply golden brown.
Let cool slightly before transferring to a cooling rack (they’re fragile when warm), then let cool completely before serving.
Emma is a writer and recipe developer at Food52. Before this, she worked a lot of odd jobs, all at the same time. Think: stir-frying noodles "on the fly," baking dozens of pastries at 3 a.m., reviewing restaurants, and writing articles about everything from how to use leftover mashed potatoes to the history of pies in North Carolina. Now she lives in Maplewood, New Jersey with her husband and their cat, Butter. Stay tuned every Tuesday for Emma's cooking column, Big Little Recipes, all about big flavor and little ingredient lists. And see what she's up to on Instagram and Twitter at @emmalaperruque.