I made cupcakes for my wedding to make it fun for all the kids there and to make it easier to portion the cake. Rich Melman, one of my restaurant partners, stopped by the reception and loved the idea and then said I should bake them someday in cups and then they'd really be "cup cakes." I don't think he thought I would ever do it, but here it is. I think it's fun to top them with whipped cream to look like a cup of hot cocoa or you could place mini marshmallows on top and broil it to give it a toasted marshmallow top. You could also do these mini for even more kid-fun!
Sift together the sugar, flour, cocoa, baking powder, baking soda, and salt. Transfer to a standing mixer fitted with a whisk attachment (or use a hand mixer) and blend briefly.
Whisk together the eggs, milk, oil, and vanilla in a medium bowl. Add to the dry ingredients and mix at low speed for 5 minutes. Gradually add the hot water, mixing at low speed until just combined. The batter will be quite thin.
Pour the batter into coffee cups and arrange them 1-inch apart on a sheet pan or a rectangular cake pan. Bake until a toothpick inserted in the center comes out clean (a few crumbs are okay), and the center feels firm to the touch, about 25 to 30 minutes. Let the cakes cool on the pan. (Don't remove the cakes from the cups!)
Meanwhile, make the Topping: In a chilled bowl, combine the cream and sugar and whip, using a hand-mixer, until soft peaks form.
When ready to serve, spoon the topping over the cakes to cover, so they look like a cups of cocoa topped with whipped cream. Serve with a spoon.