In a microwavable bowl, combine Andes Mint chips and chocolate chips.
Microwave for 3-4 minutes, or until melted.
Pour Chex cereal in a large mixing bowl.
Pour melted chocolate over top of cereal and gently stir until cereal is completely coated in chocolate. Put powdered sugar and finely crushed thin mints (I used my food processor to crush mine) in a large Ziploc bag.
Add chocolate covered cereal to the Ziploc bag with powdered sugar mixture and shake until cereal is covered.
Add Mint M&Ms and more crushed thin mints, if desired.