Preheat your oven to 300°F (150°C). Spread the 1/2 cup red velvet cake mix on a parchment-lined baking sheet. Bake for about 5 minutes, stirring once, then let it cool completely. This step helps make the cake mix safer to eat since it contains raw flour.

Pour 8 cups of Chex cereal into a large mixing bowl. Use the biggest bowl you have so you can gently toss without crushing the cereal too much.

In a microwave-safe bowl, combine 1 1/2 cups white chocolate chips and 4 tablespoons unsalted butter. Microwave in 20–30 second bursts, stirring after each, until smooth and melted. Do not overheat, as white chocolate can burn quickly.

Once the mixture is smooth, whisk in the cooled, heat-treated 1/2 cup red velvet cake mix, 1/4 cup cocoa powder, 1 teaspoon vanilla extract, and 1/4 teaspoon fine sea salt until evenly blended and a rich red-brown color. If the mixture is too thick to pour, stir in 1–2 teaspoons of vegetable oil to loosen.

Pour the warm red velvet white chocolate mixture over the Chex cereal. Using a rubber spatula, gently fold and stir until every piece of cereal is evenly coated.

Transfer the coated cereal to 1–2 large zip-top bags. Add 1 1/2 cups powdered sugar, seal the bags well, and shake until the cereal is evenly covered and no longer sticky. For a thicker coating, add an extra 1/4 cup powdered sugar and shake again.

Pour the muddy buddies onto a parchment-lined baking sheet. While still slightly tacky, sprinkle with 2–3 tablespoons red sanding sugar or red sprinkles so they adhere. Toss in 1/2 cup mini white chocolate chips or red/white M&Ms if using, and gently stir to distribute.

Let the red velvet Chex mix sit at room temperature for 15–20 minutes, or until completely cool and dry to the touch. Break apart any large clumps, then transfer to a serving bowl or an airtight container for storage.