Preheat your oven to 350°F if using raw pistachios.
Spread the pistachios on a baking sheet and roast for about 8-10 minutes, or until fragrant and lightly golden. Let them cool for a few minutes.
In a food processor, combine the roasted pistachios, honey or maple syrup (if using), and salt.
Process for about 5-10 minutes, scraping down the sides as necessary, until the mixture becomes smooth and creamy.
If the mixture is too thick, add neutral oil one tablespoon at a time until you reach your desired consistency.
Taste and adjust the sweetness or saltiness as needed.
Once finished, transfer the pistachio butter to a clean jar and store it in the refrigerator for up to 2 weeks.