Preheat oven to 350.
In a large mixing bowl combine cocoa powder, flour, brown sugar, baking powder, baking soda, and salt.
In a separate bowl combine eggs, milk, peppermint extract, vinegar, and vegetable oil.
Add the wet mixture to the dry in small batches until completely mixed.
Grease the wells of 2 standard doughnut pans. Spoon batter into pans until wells are 3/4 full.
Bake for 12-15 minutes or until cooked through. Let doughnuts cool completely, preferably in pan.
To prepare the icing, melt chocolate in microwave or on double boiler. Mix in coconut oil. Dip doughnuts into chocolate then place on a cooling rack. Top with crushed peppermint candy. Let chocolate harden, then enjoy!