Place butter, confectioners' sugar, and vanilla extract in a large bowl. Beat with a medium-speed electric mixer until the mixture is smooth, about 1 minute. Do not beat until light and fluffy. Add the flour, and mix on low speed only until the flour disappears into the dough, about 1 minute. Don't work the dough much once the flour is incorporated. Fold in the pistachios and dried cranberries with a wooden spoon (See Tip 3)
Transfer the dough to a gallon-size Ziploc bag. Put the bag on a flat surface. Leaving the top open, roll the dough into a ¼-inch thick rectangle that completely fills the bag. As you roll, turn the bag occasionally and lift the plastic from the dough so that it doesn't cause creases. Seal the bag, and place in the refrigerator or freezer for at least 2 hours, or up to 2 days in the refrigerator, or up to 3 months in the freezer. (See Tip 4)
Preheat oven to 325°F. Line a large baking sheet with a silicone liner or parchment paper.
Put the Ziploc bag on a cutting board and slit it open. Discard the bag and turn the firm dough onto a parchment-lined board or counter. Using a ruler as a guide and a serrated knife, cut the dough into 1-½ inch squares. Transfer the squares to the prepared baking sheet.
Bake in the preheated 325°F oven for 25 to 30 minutes or until the edges are lightly browned. Remove from the oven; transfer to a wire rack to cool completely. Store in an airtight container.
Yield: 30 cookies.