In a large mixing bowl, combine 5 cups of Rice Chex cereal with 1.5 cups of broken mini pretzels. Gently stir until evenly distributed.
Melt 1.5 cups of semisweet or dark chocolate chips and 1.5 cups of creamy peanut butter until smooth.
Pour the melted mixture over the Rice Chex and pretzels, folding gently until coated.
Transfer to the refrigerator and chill for about 30 minutes.
In a separate bowl, mix ½ cup of powdered sugar with half of the chilled mixture, then sprinkle ½ cup more on top and toss.
Return to the refrigerator for another 60 minutes until fully set.
Sprinkle more powdered sugar as desired, then fold in the M&Ms and peanut butter cups.
Serve in a decorative bowl or package in festive bags for gifting.