Melt the butter and peanut butter in a large pot over low heat.
Add 15 ozs of mini marshmallows and stir constantly until the mini marshmallows are completely melted.
Add the cornflakes and stir until thoroughly coated after removing from heat.
Add the remaining mini marshmallows and peanut butter morsels and fold them together gently.
Using a large cookie scoop, drop 15 peanut butter cornflakes balls of equal size onto a baking sheet lined with parchment paper.
Grease your fingertips and spread the cookies to a thickness of about 1 inch.
Pack them so that they are not too dense.
Melt the peanut butter morsels and oil in 30-second increments, stirring between each, in the microwave.
Pour the mixture into a resealable bag, cut a small hole in the top of the bag, and drizzle peanut butter over each cookie.
Before serving, let set for 25 to 30 minutes.