Add all the pistachios to a food processor. Process on low until the pistachios are blended into a crumbly, sand like texture.
Once you reach this texture, scrape down the sides and turn the processor on low. Gradually pour the olive oil into the processor in a steady stream. Pause to scrape down the sides and repeat until a smooth and creamy nut butter forms.
Pour into a jar and store in a cool, dry place. This will keep for about 1-2 weeks.