Special equipment: 9 by 9 inch baking pan
Preheat the oven to 350 degrees F.
Cream the butter and sugar together until light and fluffy. Add the vanilla extract and mix for 30 seconds. Next add the flour and espresso powder and mix until the dough is smooth, about 1 minute.
Spray the shortbread pan with cooking spray and scatter the ground espresso across the bottom of the pan. Gently press the dough evenly into the espresso covered pan. Place the pan into the top half of the oven and bake until the shortbread is set, about 18 to 20 minutes. Remove from the oven and let cool 15 minutes.
Using a sharp paring knife score the top of the still warm but cooling short bread. Cut in any size you prefer, we like 2 inch squares. Run a butter knife around the edge of the pan and invert onto a cutting board. Give 1 sharp rap and the shortbread will release from the pan. Let cool an additional 10 minutes and slice along the scored lines.