Preheat the oven to 350 degrees F. Line two baking sheets with parchment paper.
In a small microwave-safe bowl, combine the bittersweet chocolate and butter and microwave in 30-second intervals, stirring after each, until melted.
In a large bowl, stir together the eggs, vanilla, and 1/2 cup of the granulated sugar. In another large bowl, whisk together the flour, baking powder, and espresso powder.
Add the melted chocolate to the egg mixture. Slowly add the flour mixture.
Add the semisweet chocolate chips to the batter. Chill the dough for 20 to 30 minutes.
In a medium bowl, combine the peanut butter and confectioners’ sugar. Using your hands, shape into 1-inch balls and set aside.
Using a cookie scoop, shape the dough into 2-inch balls and place on the prepared baking sheets about 2 inches apart. Bake for 10 minutes, until they start to set up. Do not overbake.
Remove the cookies from the oven. While the cookies are still warm, press one peanut butter ball into the center of each cookie, allowing them to flatten and spread without hitting the edges.
Cool for 5 minutes, then transfer to a wire rack to cool completely. Serve.
