Preheat the oven to 350 degrees Fahrenheit.
Line a baking sheet with parchment paper. Spread the pistachios on it in a single layer and roast the pistachios for about 8-10 minutes.
When the time is up (the pistachios should be quite fragrant at this point) remove the baking sheet with the roasted pistachios from the oven and set it aside for 10 minutes for the pistachios to cool down.
Next use a high-speed blender or food processor to grind the roasted pistachios. Grinding them into pistachio butter will take about 15-20 minutes. During the process, turn the blender/food processor off and scrape down the ground pistachios that will tend to line the sides of the blender/food processor.
When the pistachio butter is at a creamy, butter-like consistency that you prefer, add in a pinch of salt and grind it a few more seconds.
Then, using the rubber spatula, scrape the pistachio butter into glass jars.
Enjoy with toast or pancakes, make pistachio milk, or in your favorite baked and frozen treats!