Butter/grease and flour a 12x18x1-inch baking sheet.
In the top of a double boiler over simmer watering melt together the butter, 1 pound of chocolate chips, and the unsweetened chocolate. Allow to cool slightly.
Stir together (do not beat) together the eggs, coffee granules, vanilla, and sugar in a large bowl.
Stir the warm chocolate mixture slowly into the egg mixture and allow to cool to room temperature.
In a separate bowl, sift together 1 cup of flour, the baking powder, and salt. Add to the cooled chocolate mixture. (I sift over the cooled chocolate mixture while I stir it in) Stir to combine and do not over mix.
Toss the walnuts and 8 ounces of chocolate chips in a bowl with 1/4 cup of flour, then add them to the chocolate batter. Again stir to combine and do not over mix.
Pour into the prepared 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 and refrigerate. Cut into serving pieces.
After cut into serving pieces, sprinkle with powdered sugar and serve with a small scoop of vanilla ice cream. Enjoy!