Put the semi-sweet chocolate chips, peanut butter, and butter into a microwave-safe bowl. Microwave in 30-second intervals, stirring after each one until chocolate is smooth.
Pour the chocolate peanut butter over your Chex and gently stir until all of the pieces are nicely coated.
Now it’s time to add the powdered sugar. I like to sift mine so that it doesn’t have any clumps, but if you don’t want to go to the trouble, just dump it in. Mix until all of the Chex cereal pieces are nicely coated. If you need to add a little more powdered sugar, go right ahead.