Preheat your oven to 350 degrees F. Grease inside the cups of a standard muffin pan or line with paper liners.
Place the cereal in a zip top bag and crush with a rolling pin until coarsely crumbled. You can also use a food processor, if you prefer. Combine the crushed cereal and milk in a small bowl and set aside.
Mix the flour, brown sugar, baking soda, salt, and cocoa powder in a medium bowl.
Add the egg, vegetable oil, vanilla extract, and the cereal and milk mix to the dry ingredients. Whisk until well combined.
Fill each muffin cup 2/3 of the way full. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean. Let cool.
Notes
** Nutritional information is an estimate and may vary.