dark chocolate chunk espresso shortbread - Pass the Cookies

Ingredients

• 1 cup plus 2 tablespoons salted butter*, cold, cut into small pieces
• ½ cup granulated sugar
• ¼ cup light brown sugar
• 1 teaspoon vanilla extract
• 2 ¼ cups all-purpose flour
• 4 teaspoons instant espresso powder
• 6 ounces semi- or bittersweet dark chocolate, coarsely chopped
• 1 large egg
• Turbinado sugar, for rolling
• Flaky sea salt for sprinkling