Salted Chocolate Chunk Shortbread Cookies Recipe (with Video)

Ingredients

• 1 cup plus 2 tablespoons/255 grams total salted butter (2¼ sticks), cold (room temperature if you're using a handheld mixer), cut into ½-inch pieces (see note)
• 1/2 cup/100 grams granulated sugar
• 1/4 cup/55 grams light brown sugar
• 1 teaspoon vanilla extract
• 2 1/2 cups/325 grams all-purpose flour (see Tip)
• 6 ounces/170 grams semi-sweet or bittersweet dark chocolate, chopped (not too fine; you want chunks, not little shards)
• 1 large egg, beaten
• Demerara sugar, for rolling
• Flaky sea salt, for sprinkling