Preheat the oven to 325°F (163°C). Line two baking sheets with parchment paper and set aside.

Melt the bittersweet chocolate and unsalted butter together in a double boiler or in the microwave in short bursts, stirring until smooth. Set the melted chocolate aside to cool slightly.

In an electric mixer, beat the granulated sugar and eggs together until combined and slightly thickened. Add the instant coffee granules and vanilla and beat until incorporated. Scrape the bowl with a spatula.

With the mixer on low, slowly pour the melted chocolate into the egg-sugar mixture and mix until combined. Add the baking powder and salt and mix briefly. Scrape the bowl.

Add the all-purpose flour and cocoa powder slowly and mix just until incorporated. Scrape the bowl again and avoid overmixing.

Stir in the toffee bits, reserving 1/4 cup for topping.

Form the dough into 1-tablespoon balls and place them on the prepared baking sheets about 2 inches apart. The dough will be very soft; flour your hands if needed to shape the balls.

Bake for 11–12 minutes. Immediately after removing the cookies from the oven, sprinkle the reserved 1/4 cup toffee bits on top. Allow the cookies to cool on the baking sheets.