Preheat oven to 350 degrees F.  Line two baking sheets with parchment paper.  Set aside.

In a food processor, blend 1/2 cup of shelled pistachios, flour and granulated sugar until crumbly.  Set aside.  Using a hand-held or standing mixer, cream butter and brown sugar until smooth. Beat in egg and vanilla.  Add flour mixture, baking powder and soda and salt until just combined.  Stir in 1 cup of chocolate chips and remaining 1/2 cup chopped pistachios.  Scoop dough using a large tablespoon or ice cream scoop (3 T. size) onto prepared baking sheets.  Press dough down to about 1/2-inch thick.  Bake for 11-14 minutes or until edges are barely browned.  Cool on a wire rack.

In a microwave safe bowl, combine  1 cup chocolate chips and 1 T. shortening. Microwave for about 90 seconds and stir until smooth.  Dip half of each cooled cookie into melted chocolate.  Sprinkle with 1/4 cup chopped pistachios.  Cookies will keep in a tightly sealed container for up to 1 week at room temperature.  Cookie dough and baked cookies can be frozen in a freezer-safe container for up to 3 months.