Preheat the oven to 350 degrees. Use a little butter and flour to grease then dust the inside of two 8 1/2-inch-by-4 1/2-inch loaf pans, then line the bottoms with parchment paper.

Pour the boiling water into a 2-cup liquid (glass) measuring cup, then add the bittersweet chocolate, cocoa powder and coffee granules, stirring until smooth. Let cool for 15 minutes.

Sift together the 2 cups of flour, the baking powder and salt in a bowl. Combine the walnuts, chocolate chips and the remaining 2 tablespoons of flour in a separate bowl.

Combine the 16 tablespoons of butter and both sugars in the bowl of a stand mixer or handheld electric mixer; beat on medium speed for 2 minutes. Reduce the speed to low; add the eggs one at a time, and then the vanilla extract, stopping to scrape down the sides of the bowl as needed.

Alternating in thirds, add the flour mixture and the melted chocolate mixture, beginning and ending with the dry ingredients, to form a thick batter. Stir in the nut/chips mixture by hand, until evenly distributed.

Divide the batter evenly between the pans; bake (middle rack) for 50 to 60 minutes, until a toothpick inserted in the center comes out clean. (Test in a few places, because you may poke into a melted chocolate chip.) The tops may crack; that’s okay. Cool in the pans for 30 minutes, then loosen the edges of the cakes with a rounded knife to turn out the cakes onto a wire cooling rack. Discard the parchment.

Cool to room temperature before slicing or storing.