Salted butter chocolate chunk shortbread
From Alison Roman
1 cup plus 2 tablespoons (2¼ sticks) cold salted butter, cut into ½-inch pieces
½ cup granulated sugar
¼ cup (packed) light brown sugar
1 teaspoon vanilla extract
2¼ cups all-purpose flour
6 ounces semisweet or bittersweet dark chocolate, chopped (but not too fine, you want chunks, not thin shards of chocolate)
1 large egg, beaten to blend
Demerara sugar (for rolling)
Flaky sea salt
Using an electric mixer and a medium bowl or a stand mixer fitted with the paddle attachment, beat butter, granulated sugar, brown sugar, and vanilla on medium-high speed until super light and fluffy, 3–5 minutes.
Using a spatula, scrape down sides of bowl. With mixer on low speed, slowly add flour, followed by chocolate chunks, and beat just to blend.
Divide dough in half, then place each half on a large piece of plastic wrap. Fold plastic over to cover dough and protect your hands from getting all sticky. Using your hands (just like you’re playing with clay), form dough into a log shape; rolling it on the counter will help you smooth it out, but don’t worry about getting it totally perfect. Each half should form logs that are 2–2¼" in diameter. Chill until firm, about 2 hours.
Preheat oven to 350°. Line a rimmed baking sheet (two, if you’ve got 'em) with parchment paper. Brush outside of logs with egg wash. Roll logs in demerara sugar (this is for those really delicious crispy edges).
Slice each log into ½"-thick rounds. Arrange on prepared baking sheet about 1" apart (they won’t spread much). Sprinkle with sea salt. Bake cookies until edges are just beginning to brown, 12–15 minutes. Let cool slightly before eating them all.
Do Ahead: Cookie dough can be made 1 week ahead. Tightly wrap in plastic and chill, or freeze up to 1 month. Cookies can be baked 5 days ahead. Store in plastic wrap or an airtight container.