1) To make the cupcakes: Line two muffin or cupcake pans with papers, and lightly grease the papers. If you only have one pan, you'll need to bake in shifts. Preheat the oven to 350°F.
2) Melt the butter; stir in the cocoa and hot water.
3) In a separate bowl, combine the flour, sugar, baking soda, espresso powder, and salt.
4) Blend the buttermilk or yogurt, eggs, and vanilla. Pour the cocoa mixture and the yogurt mixture over the dry ingredients, beating till smooth.
5) Pour a scant 1/4 cup of batter into each cup; a level muffin scoop works well here. Bake the cupcakes for 23 to 25 minutes, or until a cake tester or toothpick inserted into the center of one of the middle cupcakes comes out clean. Remove them from the oven and cool on a rack.
6) To make the icing: Sift the confectioners' sugar into a bowl, and stir in the cream. Mix till smooth. Add peppermint oil or extract to taste.
7) Spread the icing over the cooled cupcakes. Garnish with crushed peppermint candies, if desired. Or center a pressed-sugar holiday decoration atop each cake.
Yield: 21 cupcakes.