1. Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners.
2. In a mixing bowl, combine flour, sugar, cocoa powder, baking powder, and salt.
3. In another bowl, whisk together eggs, milk, melted butter, and vanilla extract.
4. Gradually mix the wet ingredients into the dry ingredients until well combined.
5. Fold mini M&Ms into the batter to distribute them evenly.
6. Spoon the batter into the cupcake liners, filling each about two-thirds full.
7. Bake for 18-22 minutes or until a toothpick inserted into the center comes out clean.
8. Remove the cupcakes from the oven and let them cool in the pan for a few minutes.
9. Transfer the cupcakes to a wire rack to cool completely.
10. Prepare vanilla buttercream or chocolate frosting while the cupcakes are cooling.
11. Frost each cupcake with a piping bag or a spatula once they are completely cooled.
12. Decorate the tops with more M&Ms for a colorful and fun finish.
13. Serve the M&M cupcakes at birthdays, parties, or celebrations.
14. Store any leftovers in an airtight container to keep them fresh.