stir it every 10 minutes). Meanwhile, using your 1-inch round cookie cutter
or an apple corer, cut the centers out of the cooled cupcakes. You want to go
most of the way down the cupcake but not cut through the bottom — aim for 2/3 of
the way. A slim spoon or grapefruit knife will help you get the center out.
Those are your “tasters”. Put the ganache into a piping bag with a wide tip and
fill the holes in each cupcake to the top.
Make the frosting: Whip the butter in the bowl of an electric mixer,
or with a hand mixer, for several minutes. You want to get it very light and
fluffy. Slowly add the powdered sugar, a few tablespoons at a time.
[This is a fantastic trick I picked up while working on the cupcakes article
for Martha Stewart Living; the test kitchen chefs had found that when they added
the sugar slowly, quick buttercream frostings got less grainy, and tended to
require less sugar to thicken them up.]
When the frosting looks thick enough to spread, drizzle in the Baileys (or
milk) and whip it until combined. If this has made the frosting too thin (it
shouldn’t, but just in case) beat in another spoonful or two of powdered
sugar.
Ice and decorate the cupcakes. [I used a star tip and made little "poofs"
everywhere and sprinkled it with various colors of sanding sugar to keep it
looking festive for New Years. I bet shaved dark and white chocolates would look
gorgeous as well.]
Do ahead: You can bake the cupcakes a week or two in advance and store
them, well wrapped, in the freezer. You can also fill them before you freeze
them. They also keep filled — or filled and frosted — in the fridge for a day.
(Longer, they will start to get stale.)