makes 24 cookies
1 cup (8 ounces or 225 grams) salted butter, cold, cut into small pieces
1/3 cup (65 grams) granulated sugar
1/3 cup (70 grams) light brown sugar
1 teaspoon (5 ml) vanilla extract
2 cups (260 grams) all-purpose flour
5.5 to 6 ounces (155 to 170 grams) semi- or bittersweet dark chocolate, chopped into chunks, see Note below
1 large egg or 1 large egg white (either works)
Turbinado sugar, for rolling
Flaky sea salt for sprinkling
Make the cookie dough with a stand mixer:
Beat the butter, granulated and brown sugars, and vanilla with a stand mixer, bowl locked, until light and fluffy, scraping down the bowl as needed and mixing until no buttery chunks remain. Add flour, and mix just until combined and all flour is moistened. Add chocolate chunks, mix just until incorporated. Mixture will look crumbly.
Make the cookie dough with a handmixer:
Use the same process, but you’ll want to start with room temperature or softened butter.
Shape and chill the dough:
Transfer dough to a large sheet of parchment paper (mine is 13×18 for a half-sheet pan) and form into a log the long way about 2.25 to 2.5 inches in diameter. Chill until totally firm, about 2 hours.
Slice and finish the cookies:
When you’re ready to bake the cookies, heat your oven to 350°F. Line one or two large baking sheets with parchment paper. Lightly beat the egg and open up your chilled cookie logs to brush it over the sides. Sprinkle the coarse sugar on the open paper or plastic wrap and roll the logs into it, coating them.
Using a sharp serrated knife, cut logs into 1/2-inch thick rounds. You’re going to hit some chocolate chunks, so saw gently, squeezing the cookie to keep it from breaking if needed. If they break, just squeeze it back together in a disc-like shape. Once baked, they hold together.
Bake the cookies:
Arrange cookie slices on prepared sheets one inch apart (they don’t spread much) and sprinkle each with a few flakes of salt. Bake for 12 to 15 minutes, or until the edges are just beginning to get golden brown. Let cool slightly to set before transferring the cookies you don’t eat immediately to wire racks to cool the rest of the way.
Do ahead:
The dough can be made ahead and stored, tightly wrapped in plastic, up to 1 week in the fridge, or 1 month in the freezer. Baked cookies keep in an airtight container for 5 days