Preheat oven to 325F with the rack in the middle position.
Line an 8 or 9 inch square baking dish with parchment paper, with at least two edges hanging over the dish (this will make it much easier to remove the cookies later).
In a food processor, add the flour, sugar, salt, and coffee granules. Pulse together a few times to mix.
Add the butter chunks around the flour and pulse again until the dough starts to come together. Do not over process. It should still look crumbly.
Press the dough across the bottom of the baking dish inn an even layer. Prick the dough all over with a fork.
Bake until the cookies are just golden brown, approximately 35-40 minutes. (An 8 inch pan may take 5-10 minutes longer as the dough is thicker).
Place the baking dish on a wire rack to cool. While still warm but not hot, remove the bars from the dish using the edges of the parchment paper. Cut into pieces (to get the triangles, cut the square into 3x3 squares first, then diagonally across the squares to get 18 triangles).
You can also make this by hand by pinching the butter into the flour mixture, or using a pastry cutter or fork. If it gets too warm from your hands, chill for a few minutes before continuing.It is important to cut while still warm to minimize breaking and crumbling as the dough is very tender.