In a large bowl, combine flour, sugar, cocoa powder, baking soda, baking powder, and salt. Add egg, yogurt, and oil, and lightly mix. Add water and vanilla; mix until just incorporated. Expect the batter to be pourable.
Preheat oven to 350 F. Line a 12-cup muffin tin with paper liners. Evenly divide batter between cups. Bake 18 to 20 minutes. Set aside to cool completely.
With an electric mixer, beat butter and powdered sugar, on low at first then on medium until combined. Mix in vanilla and 1/8 teaspoon of the peppermint extract. Taste test before adding another 1/8 teaspoon of peppermint, plus a small amount of food coloring at a time until desired color is reached. Mix in a bit of milk to thin if needed for easy piping. When cupcakes are cool, pipe 3 or 4 frosting “trees” at a time and sprinkle them with “ornaments.”
Per serving: 464 calories, 22 grams fat (11 grams saturated fat), 67 grams total carbohydrates, 54 milligrams cholesterol, 163 milligrams sodium, 1 gram fiber, 3 grams protein.
