01 - Preheat oven to 350°F. Line a 12-cup muffin tin with cupcake liners.
02 - In a large bowl, whisk together flour, cocoa powder, sugar, baking powder, baking soda, and salt.
03 - In a separate bowl, whisk eggs, milk, vegetable oil, vanilla extract, and peppermint extract until combined.
04 - Add wet ingredients to dry ingredients and mix until just combined.
05 - Gradually pour in hot water while whisking until batter is smooth and thin.
06 - Divide batter evenly among liners, filling each about two-thirds full.
07 - Bake for 18 to 20 minutes or until a toothpick inserted in the center comes out clean.
08 - Let cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
09 - Beat softened butter until creamy. Add powdered sugar, milk, peppermint extract, and salt; beat until light and fluffy.
10 - Spread frosting over cooled cupcakes and garnish with crushed peppermint candies if desired.