Instructions

• Preheat oven to 350°F. Line two baking sheets with parchment paper and set aside.
• Beat the room-temperature butter until smooth.
• Add the packed brown sugar, the 2 tablespoons sugar, the molasses, and the vanilla; beat until well blended.
• Add the room-temperature egg and mix until fully combined, scraping the bowl sides as needed.
• Sift together the flour, the Dutch-process cocoa powder (1/2 cup plus 1 tablespoon), and the salt. Add the sifted dry ingredients to the butter mixture and mix just until incorporated—do not overmix.
• Stir in the bittersweet chocolate pieces and the semisweet chocolate pieces until evenly distributed.
• Let the dough rest at room temperature for 5–10 minutes, or cover and chill in the refrigerator for 1 hour to help prevent flat cookies.
• Drop rounded teaspoons of dough onto the prepared baking sheets, spacing them about 2 inches apart.
• Bake at 350°F for about 9 minutes, or until the cookies are just firm at the edges and slightly soft in the centers.
• Cool the cookies on the baking sheets for about 5 minutes, then transfer them to a wire rack to finish cooling.