Easy, easy, easy!
Get the nicest, fattest peanuts; remove the skin if there is any. A food processor is the easiest way to do this, or you could even mash them by hand if you have to. Mash up the peanuts, adding the tiniest drizzle of oil (vegetable is fine) until you think it's the right consistency. Refrigerate. When you want some pb put the amount in a small bowl to warm up a bit.. Voila!