In a large bowl add cereal and set aside.: The cereal should look fresh, pale, and crisp, and when you pour it you will hear a light, dry rustle. Take a moment to break any large clumps with your fingers so the outer surface area is even for coating. This prevents uneven pockets later when the chocolate mixture adheres. A common mistake is using stale cereal which will result in a limp final texture, so smell the cereal first, it should smell clean and not musty.
In a saucepan over low heat, melt the chocolate and butter; add peanut butter and mix until smooth or in a microwavable bowl add chocolate chips, peanut butter and butter. Microwave uncovered on high for 1 minute; stir. Microwave about 30 seconds longer or until mixture can be stirred smooth.: As the chocolate melts you will notice it loosening and a glossy sheen appearing, and the scent of warm chocolate will deepen. Keep the heat low to avoid seizing, stir continuously with a silicone spatula so the butter and peanut butter emulsify into a smooth, shiny sauce. The reason for gentle heat is to preserve the silky texture and prevent graininess, which ruins the mouthfeel. If you overheat it may smell slightly burnt, which is a sign to start over or lower the heat immediately to rescue it.
Stir vanilla extract into chocolate mixture. Pour over cereal in a bowl. Stirring until evenly coated. Pour into a 2-gallon resealable food storage plastic bag.: If you choose the microwave route, listen for no sudden popping noises, and stop to stir when the center looks partially melted. The movement of the spatula should be smooth, and you will see the mass become glossy. Microwaves vary, so the initial minute is a starting point; if the mixture still holds solid chips, continue with short bursts to avoid overheating. A common pitfall is leaving it too long, which causes the chocolate to separate and become gritty.
Add powdered sugar into a large plastic bag and shake until well coated.: After the short bursts, the mixture should stir into a cohesive ribbon when lifted with a spoon, and steam may rise gently. The tactile cue is a velvety, pourable consistency. If it seems thick, a tiny splash of neutral oil can help, but usually patience and short stirring intervals will do the trick. Avoid adding water as it will cause the chocolate to seize.
Spread on waxed paper to cool completely. After it is completely cooled add in M&Ms and peanut butter cups, gently stir to combine.: The tiny addition of vanilla extract will bloom the aroma, creating a warmer scent profile and rounding the edges of sweetness. Immediately after adding it, stir briskly so the vanilla distributes evenly and does not concentrate in one area. If you notice any separation after adding vanilla, continue gentle stirring off heat until it reincorporates. A mistake is adding strong flavorings too early, which can evaporate or become muted.
Store in an airtight container.: When you pour the warm chocolate-peanut sauce over the bowl of crispy rice cereal squares , you will hear a satisfying soft crackle as the sauce hits the cereal. Use a large spoon or spatula and fold gently so every piece gets a light, even coat. The goal is glossy coverage without saturating, which keeps the cereal crisp. If you rush and overmix vigorously, the clusters will break down and become powdery.
Pour into a 2-gallon resealable food storage plastic bag.: Moving the coated cereal into a roomy bag makes the next step tidy. The bag should be only partially filled so there is room to shake without spilling. This technique lets you control the amount of confectioners sugar that clings to each cluster. Filling the bag too full will prevent even coating and can cause tearing or spilling.
Add powdered sugar into a large plastic bag and shake until well coated.: When you add the confectioners’ sugar , seal the bag and shake gently, then more vigorously, until the cereal pieces look uniformly dusted like tiny snowballs. The sugar will absorb any residual oil and create the signature dry, powdery finish. If some clumps form, open the bag and give a careful stir to break them up. Too little shaking leaves uneven sweetness, while too rough shaking crushes the clusters.
Spread on waxed paper to cool completely.: Lay the coated mixture on waxed paper in a single layer and allow it to cool to room temperature. Visually you want the coating to lose its shine and feel dry to the touch. Cooling here prevents the M&Ms and mini peanut butter cups from melting when added. If you rush this step and add candies while warm, their colors may bleed and the texture will be compromised.
After it is completely cooled add in M&Ms and peanut butter cups, gently stir to combine.: The final fold should be gentle enough to preserve the shape of mini peanut butter cups and the candy shells on the M&Ms . The sound will be a soft rustle, and the visual should be a festive scatter of red and green among snowy clusters. One mistake is stirring too roughly, which can smash the minis and create sticky patches, so take your time and use a wide bowl for more control.
Store in an airtight container.: Once cooled and mixed, transfer the finished Reindeer Chow to an airtight container. The container keeps the exterior coating crisp and prevents the mix from absorbing pantry odors. Store at room temperature for up to two weeks, or longer if you keep it sealed and cool. Beware of humidity, which is the main enemy; if stored in a warm, damp place the coating can soften and lose its powdery finish.