Soak the shelled pistachios in water for about 30 minutes, then drain and chop coarsely.

Cream the softened butter and granulated sugar together in the bowl of a stand mixer for 3-4 minutes until light and fluffy.

Incorporate the room temperature egg and mix until well combined. Gradually sift in the all-purpose flour and add the chopped pistachios, mixing until just combined.

Transfer the dough onto a lightly floured surface, knead a couple of times, divide into two logs, wrap in plastic wrap, and refrigerate for at least 2 hours.

Preheat the oven to 350°F (175°C). Slice the chilled dough into rounds about ¼ inch thick and arrange on a baking sheet lined with parchment paper.

Bake for 10-12 minutes until golden, then let cool on a wire rack.

Melt the dark chocolate, dip half of each cookie in it, and let set on a parchment-lined baking sheet.