To make pistachio flour (If you already have some, skip to the next section.)
Reserve ¼ cup of the pistachios, then dump the rest in a food processor with the blade attachment.
Blitz the pistachios til very fine ground. Don’t take them too far, though, or you’ll have pistachio butter.
Run the grounds through a sieve and return what remains to the food processor.
Repeat three times or until you have ¾ cup of pistachio flour. If you’re coming up short, just use more of the grinds to top it off.
To make dough
Wipe out the food processor, then add in the butter and sugar. Cream together, then add salt.
Dump in pistachio flour and all-purpose flour and pulse the mixture until it is starting to come together. Scrape down the sides and bottom with a rubber spatula to make sure everything is incorporated.
Add the chopped cranberries and pulse again until it forms a cohesive dough.
Dump out onto a work surface and divide equally into two. Form the two dough masses into 8-inch logs and roll them up tightly in plastic wrap. Refrigerate for at least an hour.
Once the dough logs have chilled and firmed up, preheat the oven to 350° F.
Cut about 15 rounds from each log, aiming for just under a half-inch in thickness. Organize rounds on two parchment-lined baking sheets.
Bake the trays for 18 minutes, rotating them and switching their places halfway through.
Let cookies rest on the baking sheet for five minutes, then transfer to a wire rack to cool completely.
Assemble
While the cookies are cooling, melt the white chocolate in a double-boiler (a metal or glass bowl placed over—but not touching— about an inch of simmering water in a pot).
Chop up the remaining pistachios into bits.
Dip a cooled cookie one-third of the way into the white chocolate, then transfer to a piece of parchment. (If you don’t want so much white chocolate, just spoon some over one side of the cookie in stripey-streaks.)
Sprinkle with the chopped pistachios. Repeat!