Before getting started, preheat your oven to 350ºF. Be sure to chop up the pistachios and cranberries with a large knife, and then line a 13x9 baking sheet with parchment paper.
In a large mixing bowl or in the bowl of an electric stand mixer, beat the softened butter with a fork until fluffy.
Next, add the sugar and salt to the butter, mixing 'til well combined and fluffy.
Beat the egg and vanilla into the butter mixture 'til well combined.
Now, gradually add the flour a little bit at a time, mixing until well combined.
Finally, add your chopped cranberries and pistachios to the cookie dough, mixing well.
Use the palm of your hand to roll the cookie dough into little balls, and place them onto the prepared cookie sheet. It helps to spritz some nonstick cooking spray onto your hands before you do this.
Bake your white chocolate pistachio cookies for 8-10 minutes at 350ºF, or 'til the edges are set and slightly golden brown.
Once they're fully baked, transfer your cookies to a wire rack and let cool to room temperature.
Once your cookies have cooled completely, melt the white chocolate chips in a microwave safe bowl in the microwave.
Drizzle your cookies with the melted white chocolate, and let them set for 5-10 minutes, or 'til the chocolate is hardened.
That's it. Serve and enjoy with a cold glass of milk!