This post is sort of a work in progress; it's definitely going to require some editing. UPDATE: these things are taking forever to dry. Either allow them more time to dry or use a narrower tip than a #12 if you're in a rush.
One of my favorite things about blogging is being able to see the keyword searches people have done that have led them to my blog, and lately some folks have found it by looking for goal posts to put on cupcakes (undoubtedly as a result of my post about chocolate footballs for cupcakes). Well, I figured I'd better get an idea up there sooner rather than later, so here's what I've come up with. Start by making a batch of royal icing; it should be about the thickness of toothpaste (I'd use 5 tablespoons of water, not 6). Oh, and that would be old school toothpaste, not the new-fangled stuff with stripes, glitter, gel, etc. Tape parchment paper to a cookie sheet:
I attached a Wilton #12 round tip to a disposable pastry bag using a standard coupler, so I could easily switch to a smaller round tip #8 if the #12 didn't work out:
Cuff the bag over your hand and start filling the bag with the royal icing using an offset spatula. Get a handful or so of icing in there, then unfold the cuff and give the bag a twist.
Royal icing dries hard and fast, so you want as little air in there as possible. Squeeze out a bunch of icing back into the bowl to clear out any air bubbles:
Wipe off the tip and hold the bag as close to level with the parchment paper as possible. Slowly squeeze and pull. The size of the goal post is up to you (the three short lines on mine are about 1.5" long); just make the post long enough so you can stick it into the cupcake and have it not fall over.
Here's the trick for getting those ends squared off: slide a small straight spatula in between the tip and the icing you just piped, and pull the tip away.
When you pipe each new line, be sure to butt the tip against the last line you piped, but don't squeeze so hard that the last line will become distorted. Keep a dusting pouch full of powdered sugar and cornstarch handy; touch a fingertip to it and you can gently nudge out any mistakes (preferably not with your index finger; it's too "stabby"). Allow these "goal posts" to dry overnight (they might be done sooner but they're pretty thick; they may need longer). If they break when you slide them off the parchment paper (possibly with the aid of the offset spatula, but you can probably just peel the paper away by hand), you can always make repairs with more royal icing.
As soon as I get these off the parchment, I'll post photos of the finished cupcakes. I'm sure they'll be adorable, er, intimidating and combative.