Place peanut butter into microwave safe bowl and heat in microwave for 20-30 seconds until liquid like. Stir in vegetable oil until well combined then stir in chopped Reeses Peanut Butter Cups. Drizzle over firm cold ice cream and let harden. The peanut butter shell works best if you place back in the freezer once you drizzle it over your ice cream for a few minutes.