Place pistachios in food processor and start processor. Initially the pistachios will be dry but as the nuts release their oil they will come together.
After about two and a half minutes the pistachios will form a ball. Let the food processor continue to run. The ball will eventually turn into a creamy consistency.
As more oil is released the pistachios will become creamy. The pistachios butter is done when it gets a shiny surface and has a looser texture then regular pistachios butter. This will take between 5 and 8 minutes. It will thicken into a creamy pistachios butter between 24 and 48 hours in the refrigerator.
Place pistachio butter in airtight container and store in refrigerator. Allow 24 - 48 hours for pistachio butter to thicken.