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 uniform.
03 - In a medium bowl, whisk eggs, whole milk, vegetable oil, peppermint extract, and vanilla extract until well blended.
04 - Pour wet mixture into dry ingredients and stir gently with a spatula until just combined. Avoid overmixing to maintain tenderness.
05 - Gently fold in chocolate chips, mini marshmallows, and crushed peppermint candies until evenly distributed.
06 - Divide batter evenly among muffin cups, filling each approximately three-quarters full.
07 - Top each portion with extra chocolate chips, mini marshmallows, and additional crushed peppermint candies as desired.
08 - Bake for 18 to 20 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
09 - Let muffins rest in pan for 5 minutes before transferring to a wire rack to cool completely.