In a microwave-safe bowl, combine the chopped Andes mints with the unsalted butter. Microwave this mixture on high for 1 minute, then stir gently. Return to the microwave for an additional 15 seconds if needed, until it's melted and smooth.

In a large mixing bowl, pour in the Chex cereal. Once the mint and butter mixture is ready, pour it over the cereal. Gently stir with a spatula or spoon until every piece is well-coated.

Transfer the coated cereal mixture to a large ziptop bag. Add the powdered sugar and seal the bag tightly. Shake vigorously until all the pieces are coated in powdered sugar.

Line a baking pan with parchment paper. Transfer the sugary coated cereal mixture onto the prepared pan, spreading it out evenly.

Sprinkle additional chopped Andes mints over the top. Melt the green candy melts according to package directions and drizzle over the mixture. Let it sit at room temperature until set, about 15 minutes.

Once set, break them apart into clusters or squares for serving. Enjoy or store them in an airtight container.