Combine chocolate ice cream, milk, and creamy peanut butter in a blender and blend until smooth.
Spread chocolate frosting around the top 2-3 inches on the outside of the milkshake glasses.
Press chopped Oreos, mini peanut butter cups, and chopped peanuts into the frosting on the glasses.
Drizzle chocolate syrup down the inside of the glasses in streaks.
Pour the blended milkshake mixture into the prepared glasses.
Top each milkshake with a generous layer of whipped cream.
Optionally, skewer cupcakes through straws and place on top of the whipped cream.
Decorate with additional toppings like chopped peanuts, cookies, peanut butter cups, and a final drizzle of chocolate syrup.
Serve immediately and enjoy your indulgent chocolate peanut butter shake.