Line a square baking dish with parchment paper and set aside. Place the cookies in a gallon-size ziploc bag and crush with a large wooden spoon until fine pieces form.
In a medium bowl, combine peanut butter and butter. Microwave for 1 minute and stir until creamy (microwave for 30 seconds longer, if needed). Add the crushed Oreos and candy bar pieces (if using) and mix well.
Spread into prepared dish and press evenly all around using fingers. Chill in the refrigerator for a minimum of 1 hour. Cut into small squares and serve!
Notes
Don’t limit yourself to just candy bars. If you have peanut butter cups or mini chocolates kisses, add them to the mixture. Be sure to stick to the 2 cups so the bars stick together. Sprinkle candy corn, M&M’s or chocolate chips on the top!