2 cups flour
1/2 cup Dutch-processed cocoa powder
2 tsp baking powder
1/2 tsp salt
16 ounces semisweet chocolate, chopped
2 tsp vanilla extract
2 tsp instant coffee or espresso powder
10 Tbsp unsalted butter, at room temperature
1 1/2 cups packed light brown sugar
1/2 cup granulated sugar
2 cups semisweet chocolate chips
Whisk together the flour, cocoa powder, baking powder and salt in a medium bowl; set aside.
Using a heatproof bowl, microwave the chocolate in 30 second intervals, stirring in between, until melted and smooth. In a small mixing bowl, combine the eggs, vanilla and instant coffee granules; stir well with a fork to dissolve; set aside.
In the bowl of an electric mixer, fitted with the paddle attachment, beat the butter at medium speed until smooth and creamy, about 5 seconds. Stir in the sugars and beat until combined, yet still granular, about 1 minute. With the mixer on low speed, gradually beat in the egg mixture until incorporated, about 45 seconds. Pour in the chocolate at a steady stream and continue mixing until combined, about 40 seconds. Detach the paddle and scrape down the bottom and sides of the bowl. Reattach the paddle and turn the mixer on low speed. Add the dry ingredients and mix just until incorporated. Do not overmix. Fold in the chocolate chips with a wooden spoon. Cover the bowl with plastic wrap and let stand at room temperature for 30 minutes.
Meanwhile, preheat the oven to 350 degrees F. Line two baking sheets with parchment paper or silicone liners. Scoop golf-ball sized dough-balls onto the prepared baking sheets, spacing about 1 1/2 inches apart. Sprinkle each cookie with sea salt.
Bake for 10 minutes, or until the edges of the cookies have just begun to set but the centers are still very soft. Rotate the sheets halfway through baking. Remove from oven and cool on the cookie sheets for about 10 minutes before transferring to a wire rack to cool completely. Cool the baking sheets back to room temperature before continuing with the remaining dough.