Start by greasing a 9x13 inch baking dish with a little butter or non-stick spray.
In a large saucepan, combine the sugar and light corn syrup over medium heat. Stir constantly until the mixture comes to a boil. Let it boil for 1 minute without stirring. Remove from heat and stir in the creamy peanut butter and vanilla extract until smooth.
Add the Rice Krispies cereal to the peanut butter mixture. Stir gently until all the cereal is fully coated.
Take about half of the Rice Krispie mixture and evenly press it into the bottom of the prepared baking dish.
Remove the frozen Reese’s Peanut Butter Cups from the freezer and arrange them in a single layer on top of the pressed Rice Krispie layer.
With the remaining Rice Krispie mixture, carefully press it over the top of the Reese’s Peanut Butter Cups.
Let the treats sit at room temperature for about 30 minutes to an hour, or until they are set. Once set, cut them into squares.
