Preheat the oven to 325 F. Melt the chocolate at 50% power in the microwave, in 30 second increments. Set aside to cool a bit.

Grease a 9X5 inch loaf pan, and then line it with parchment paper so that it overhangs the longer sides (see photo at bottom). Set aside.

Sift together the flour and cocoa powder. Whisk in the salt, baking powder and baking soda. Set aside.

Beat the butter and sugar until light and fluffy. Add the cooled melted chocolate and beat it in thoroughly. Add the eggs, one at a time, beating well after each. Be sure to scrape the sides and bottom of the bowl thoroughly. Mix in the sour cream and vanilla.

Add the flour mixture and room temperature coffee in 3 and 2 additions, respectively, alternating, beginning and ending with the dry mixture. Do not overmix. Gently fold in the chopped milk chocolate at the end.

Scrape (the batter will be thick) the batter into the prepared pan and smooth the top. Bake for 65-70 minutes, until a toothpick inserted into the center of the cake comes out clean (if you hit a pocket of melted milk chocolate, clean your tester and try again). Let the cake cool completely in the pan before turning it out.