They are small, simple, and utterly delicious.
255 grams salted butter, cold, cut into small pieces
100 grams granulated sugar
50 grams light brown sugar
1 teaspoon vanilla extract
295 grams flour
2 tablespoons espresso powder
170 grams semi- or bittersweet dark chocolate, chopped in chunks
Flaky sea salt for sprinkling
Beat the butter, granulated and brown sugars, and vanilla with an electric mixer until light and fluffy, scraping down bowl as needed. Add flour and espresso powder, and mix just until combined. Add chocolate chunks, mix just until incorporated. Mixture will look crumbly.
Divide between two sheets of parchment paper, waxed paper, or plastic wrap and use your hands to form the dough halves into log shapes about 2 to 2 1/4 inches in diameter. Chill until totally firm, about 2 hours in refrigerator or 1 hour in freezer.
Preheat oven to 350°F. Line one or two large baking sheets with parchment paper.
Using a sharp knife, cut logs into 1/2-inch thick rounds. You’re going to hit some chocolate chunks, so go fast. Arrange cookie slices on prepared sheets and sprinkle each with a few flakes of salt. They don’t spread too much, so you can gang up a lot of them. Bake for 15 minutes, or until the edges are just beginning to get golden brown. Let cool slightly before transferring to a rack to cool.