Place pistachios into a vitamix or other high powered blender. A food processor will work, but the time will be approximately 5 minutes longer. Starting on lowest speed, blend mixture about 30 seconds to 1 minute. Increase speed and blend about 4 to 5 minutes until smooth and creamy, scraping down sides with a rubber spatula as needed. Add oil slowly if necessary to add more creaminess.

Store in an airtight container in the refrigerator.