Put the peanuts in the bowl of a food processor fitted with the steel blade attachment and drizzle 2 tablespoons of the oil over the top. Pulse to break up the peanuts, add the salt and sugar, if using, and blend until very smooth. (For a chunky peanut butter, stop before the peanut butter reaches a smooth consistency.) You’ll need to scrape down the sides of the food processor periodically and, if the mixture is very dry, drizzle in more oil by the teaspoonful.
Store the peanut butter in an airtight container in the refrigerator for up to 2 months. If the oil separates from the peanuts, simply stir to recombine.
Notes
Homemade Honey-Roasted Peanut Butter variation
For honey roasted peanut butter, add 2 teaspoons honey after you begin to pulse the peanuts and just before adding the salt.