1. Line a large baking sheet with parchment paper and set aside. Place the rice Chex cereal in a very large mixing bowl, then add the mini marshmallows, salted peanuts, and chocolate chunks on top.

2. In a microwave-safe bowl, combine the semisweet chocolate chips, creamy peanut butter, and unsalted butter. Microwave in 20–30 second bursts, stirring between each, until smooth and fully melted.

3. Stir the vanilla extract into the warm chocolate mixture, then immediately pour it over the cereal and mix-ins. Gently fold with a spatula until most of the cereal is coated and chunky clusters start to form.

4. Transfer the coated mixture into a large zip-top bag or clean paper bag (work in batches if needed). Add the powdered sugar, seal well, and shake until all of the pieces are evenly covered and no longer sticky.

5. Spread the Chunky Muddy Buddies onto the prepared baking sheet in an even layer. Let cool at room temperature until the chocolate has fully set.

6. Once cool, break any extra-large clusters into bite-size pieces, transfer to a serving bowl or airtight container, and enjoy.