Add all ingredients for the shortbread to a stand mixer. Beat until a dough forms. Note: it's okay if the mixture is crumbly - this is normal.
Turn dough out onto a large piece of plastic wrap and use your hands to form it into a large ball. Work the dough into a cylinder. I use the plastic wrap to help keep the cylinder intact while shaping it.
Transfer cylinder of dough to the freezer and freeze at least 2 hours. When you're ready to bake, allow the dough to thaw so that it's easy to cut but is still chilled.
Preheat the oven to 350 degrees F and line a large baking sheet with parchment paper.
Slice dough into 1/4-inch to 1/2-inch rounds using a sharp knife. Place dough rounds on the parchment-lined baking sheet.
Bake 10 to 15 minutes, or until cookies are golden-brown around the edges. Remove form the oven and allow cookies to sit 30 minutes. Use a spatula to transfer cookies to a plate.
Melt chocolate chips in the microwave (microwave on high for 15-second intervals, stirring between, until melted) in a heat-safe bowl. Drizzle or spread the chocolate over the shortbread cookies. If desired, sprinkle the melted chocolate with more chopped pistachios and dried cranberries.