Now you need to work quickly, as the dough should stay as cold as possible. It's best to first quickly rub the mixture into a crumbly texture, then add the egg yolk.

Again working quickly, bring the mixture together into a smooth, soft dough. I recommend using a stand mixer, as it won't warm up the dough. Wrap the dough in plastic wrap and chill in the fridge for at least 1 hour, ideally overnight.

Before baking, line your baking trays with parchment paper. Preheat the oven to 150°C (fan) or 160°C (conventional top/bottom heat).

Roll out the dough on a floured surface and cut out shapes – always one full round and one with a cut-out center to match. Bake for 12 minutes, watching closely so the cookies don't darken too much. They should stay pale.

Once the cookies have cooled slightly on the tray, carefully transfer them to a wire rack to cool completely.

Beat the softened butter with sugar and hazelnut spread until fluffy. Dip half of each ring-shaped cookie into melted chocolate and sprinkle lightly with chopped pistachios.

Once the chocolate has set, spread the cream onto the plain (uncut) cookie halves and sandwich both pieces together.