01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners.
02 - In a large mixing bowl, whisk together flour, cocoa powder, sugar, baking powder, baking soda, and salt until evenly blended.
03 - In a separate bowl, whisk eggs, whole milk, vegetable oil, peppermint extract, and vanilla extract until thoroughly combined.
04 - Add the wet ingredients to the dry mixture and stir gently until just combined, avoiding overmixing.
05 - Gently fold chocolate chips, mini marshmallows, and crushed peppermint candies into the batter.
06 - Divide batter evenly among muffin cups, filling each about three-quarters full. Add extra chocolate chips, marshmallows, and additional peppermint candy on top as garnish.
07 - Bake muffins for 18 to 20 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
08 - Allow muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.