In a large saucepan over medium heat, melt the unsalted butter. Once melted, stir in the creamy peanut butter until well combined and smooth.
Add the mini marshmallows to the peanut butter mixture. Stir continuously until the marshmallows have completely melted and the mixture is smooth.
Remove the saucepan from heat and quickly stir in the vanilla extract and a pinch of salt.
Gradually fold in the Rice Krispies cereal until evenly coated with the peanut butter mixture, ensuring no cereal is left dry.
In a separate microwave-safe bowl, melt the semi-sweet chocolate chips in the microwave in 30-second intervals, stirring until smooth.
Pour half of the cereal mixture into a greased 9x13 inch baking dish, pressing it down firmly with a spatula.
Drizzle half of the melted chocolate over the first layer of Rice Krispies.
Spoon the remaining cereal mixture on top, pressing it down once more. Finally, drizzle the rest of the melted chocolate over the top layer, smoothing it out as needed.
Allow the treats to cool at room temperature for about 30 minutes, or until the chocolate is set.
Once set, cut into squares and enjoy!
Notes
Allow treats to cool completely before cutting for best results.