1. Preheat oven to 325 degrees F. Line baking sheets with parchment paper.

2. In a microwave-safe bowl, melt 2/3 cup dark chocolate chips on medium power for 30 seconds; stir. Morsels may retain some of their original shape. Continue to microwave and stir in 15 second intervals until chocolate chips are just melted. Set aside.

3. In a medium bowl, sift together flour, cocoa, baking soda and salt. In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl with an electric mixer, beat butter, brown sugar and granulated sugar until light and fluffy; about 3 minutes. Add melted chocolate and mix until thoroughly combined. Add egg and vanilla extract, mixing until well blended, about 1 minute. Add flour mixture, mixing just until blended. Stir in remaining 1 cup morsels. Using a medium cookie scoop (1 1/2 tablespoons) drop dough 2 inches apart onto prepared baking sheets.

4. Bake for 12 - 14 minutes until tops have a cracked appearance. Cool on baking sheets for 5 minutes. Remove to wire rack to cool completely.