Preheat the oven to 150°C. Line a baking sheet with baking paper and spread the nuts over it. Roast the nuts for 10 minutes.
Put the warm pistachios together with the fine sugar and salt in a grinder, food processor or mortar and grind it as finely as possible. During grinding, oil is released, making the paste smoother. This will take a while. The longer you grind, the finer and more liquid the pistachio paste becomes. If the pistachio paste still stays a little dry after about 10 minutes of mixing, you can add a bit of neutral oil (e.g. sunflower oil)