1. Melt the Chocolate and Peanut Butter: In a microwave-safe bowl, combine the semisweet chocolate chips and creamy peanut butter. Microwave them together in 20-second intervals, stirring well after each interval until the mixture is smooth and fully melted. Once melted, stir in the vanilla extract for added flavor.

2. Coat the Cereal: In a large mixing bowl, pour in the Rice Chex cereal. Carefully pour the melted chocolate and peanut butter mixture over the cereal. Gently toss the cereal to coat each piece evenly without crushing them.

3. Prepare the Coating: In a large resealable plastic bag, add the powdered sugar and the brownie mix. Seal the bag and shake it vigorously to mix the contents thoroughly.

4. Combine and Shake: Once your cereal is well-coated with chocolate, transfer it to the bag with the powdered sugar and brownie mix. Seal the bag tightly and shake it again until all the cereal pieces are coated evenly.

5. Cool and Serve: Spread the chocolate-coated cereal onto a baking sheet lined with parchment paper, allowing it to cool completely. After it has cooled, you can transfer it to a serving bowl or store it in an airtight container for later enjoyment.