In a microwave-safe bowl, combine the semisweet chocolate chips, creamy peanut butter, and salted butter. Microwave in 30-second intervals, stirring in between, until the mixture is completely melted and smooth. Remove from the microwave and stir in the vanilla extract.
In a large mixing bowl, pour in the Chex cereal. Carefully pour the melted chocolate mixture over the cereal. Using a spatula, gently fold the chocolate mixture into the Chex until all pieces are evenly coated.
Once the Chex is well-coated, sprinkle the powdered sugar over the mixture. Again, gently fold until all the cereal is coated in the powdered sugar, creating that signature snowy look.
Spread the Muddy Buddies onto a cookie sheet lined with parchment paper. Allow them to cool and set for about 30 minutes to an hour.
Once cooled, your Muddy Buddies are ready to be enjoyed! Store them in an airtight container to keep them fresh for snacking throughout the week.