Gather all your ingredients. Make sure your Reese's Peanut Butter Cups have been frozen for at least 30 minutes.
In a large saucepan over medium heat, combine the sugar and light corn syrup. Stir until the sugar dissolves and the mixture begins to boil. Allow it to boil for about 1 minute without stirring.
Remove the saucepan from heat and stir in the creamy peanut butter and vanilla extract until completely smooth and well blended.
In a large mixing bowl, pour the melted peanut butter mixture over the Rice Krispies cereal. Gently fold the cereal into the mixture until all the cereal is evenly coated.
Line your 9x13 inch baking dish with parchment paper, leaving some overhang on the sides for easy removal. Press half of the Rice Krispie mixture into the bottom of the prepared dish.
Place the frozen Reese's Peanut Butter Cups evenly over the first layer of Rice Krispies. Press them down slightly so they stick.
Using the remaining Rice Krispie mixture, carefully press it on top of the Reese's layer, ensuring it covers the filling completely.
Allow your treats to cool at room temperature for about 30 minutes. Once set, lift them out of the dish using the parchment paper.
Using a sharp knife, cut the treats into squares or rectangles. Serve immediately or store them for later enjoyment!
