Add peanuts to a food processor and blend until a thick nut butter forms. Stream in oil and vanilla with the processor on, continuing to run it until the mixture is smooth – this took me about 3-4 minutes. You can add more oil if needed, just do it in small increments. Turn off processor, add melted chocolate, and turn processor back on. Blend until smooth.

I kept mine at room temperature for a week, but I do recommend refrigerating the butter if you want to keep it for a few weeks.