01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners.
02 - In a large bowl, whisk together all-purpose flour, unsweetened cocoa powder, granulated sugar, baking powder, baking soda, and salt.
03 - In a separate medium bowl, whisk eggs, whole milk, vegetable oil, peppermint extract, and vanilla extract until fully blended.
04 - Pour wet mixture into dry ingredients and mix gently by hand until just combined. Avoid overmixing to retain tenderness.
05 - Fold in semi-sweet chocolate chips, mini marshmallows, and crushed peppermint candies until evenly distributed.
06 - Divide batter evenly among muffin cups, filling each approximately three-quarters full. Top with additional chocolate chips, marshmallows, and peppermint candies for garnish.
07 - Place pan in oven and bake for 18 to 20 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
08 - Let muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving.