Line an 8x8-inch baking dish with parchment paper or lightly grease it with non-stick spray. This will make it easier to remove the treats later.

In a large saucepan, melt the butter over low heat. Once melted, add the marshmallows and stir continuously until fully melted and smooth. Next, stir in the peanut butter until well combined.

Remove the saucepan from the heat and quickly stir in the crispy rice cereal. Mix until the cereal is evenly coated with the peanut butter-marshmallow mixture.

Transfer the mixture into your prepared pan. Use a spatula (or the back of a spoon) to press the mixture firmly and evenly into the pan. Let it sit and cool for about 10 minutes.

While the crispy treats are setting, melt the chocolate chips in a microwave-safe bowl in 20-second intervals, stirring in between until smooth. Pour the melted chocolate over the rice crispy mixture, spreading it evenly across the top.

Let the chocolate set at room temperature or speed up the process by placing the treats in the fridge for about 20-30 minutes. Once the chocolate is firm, lift the treats out of the pan using the parchment paper and cut them into squares.