Preheat oven to 350 degrees F.
Butter and flour a 12 x 18 x 1-inch baking sheet.
Melt together the butter, 1 pound of chocolate chips, and the unsweetened chocolate in a medium bowl over simmering water. Allow to cool slightly. In a large bowl, stir (do not beat) together the eggs, coffee granules, vanilla, and sugar. Stir the warm chocolate mixture into the egg mixture and allow to cool to room temperature.
In a medium bowl, sift together 1 cup of flour, the baking powder, and salt. Add to the cooled chocolate mixture. Toss the walnuts and 12 ounces of chocolate chips in a medium bowl with ¼ cup of flour, then add them to the chocolate batter. Pour into the baking sheet.
Bake for 20 minutes, then rap the baking sheet against the oven shelf to force the air to escape from between the pan and the brownie dough. Bake for about 15 minutes, until a toothpick comes out clean. Do not overbake! Allow to cool thoroughly, refrigerate, and cut into 20 large squares.
For the hot mess brownies:
Prepare the brownies as directions indicate. Cut brownies and place them onto a wire rack with a drip pan at the bottom to catch any chocolate or caramel that might drip down.
While brownies are cooling heat in a double boiler the chocolate and the butter until it becomes smooth and has a sheen to it.
While still slightly warm add a spoonful of marshmallow fluff onto each brownie. How many brownies you get depends on how big you cut your brownie. I cut mine pretty big.
The marshmallow will start to spread. Put a spoonful of caramel on top of the marshmallow. It will also spread a little.
Then spoon some of the chocolate on top of the marshmallow and caramel. It will spread as well but will eventually harden back up.
When the chocolate has hardened again they will be ready to serve. Clearly these are messy to eat but ridiculously good.