Chocolate Chip Angel Cupcakes

I decided to try something I've never tried before today. I've seen recipes for angel cake before, but they all seem to need to be baked in special pans. So when I came across a recipe for Chocolate Chip Angel Cupcakes on the Cooking Light website, I thought I'd give it a go.
Well, the recipe says it makes 24, but I thought I'd just make a half quantity - as it is, that made 10 cakes.
I suppose they turned out OK. They certainly taste fine. It's just, well, I guess I'm not sure quite what I was expecting. I think I may have left them in the oven too long. I certainly wasn't expecting the shrinkage and slight misshapenness of the resulting cakelets. I hadn't intended to ice them, but I changed my mind once I saw them. The icing used isn't the one in the original recipe, but a simple one made by melting butter and chocolate together (twice as much chocolate as butter) and adding icing sugar to give the desired consistency.

Recipe:
1/2 cup plain flour
3/4 cup caster sugar
6 egg whites
1/2 teaspoon cream of tartar
1/8 teaspoon salt
1 teaspoon vanilla extract
3/4 teaspoon lemon juice
50 grams dark chocolate, Green & Black's, 70%

Preheat oven to 325F/160C. Line a muffin tin with muffin cases.
Lightly spoon sifted flour into a dry measuring cup, and level with a knife. Combine the flour and 6 tablespoons sugar in a bowl.
Put egg whites in a large bowl. Beat until foamy.
Add the cream of tartar and salt. Beat until soft peaks form.
Add 6 tablespoons of sugar, 2 tablespoons at a time, beating until stiff peaks form.
Beat in vanilla extract and lemon juice.
Sift 1/4 cup flour mixture over egg white mixture; fold in. Repeat procedure with remaining flour mixture, 1/4 cup at a time.
Fold in the chopped chocolate.
Spoon 3 heaped tablespoons batter into each muffin cup. Bake for 15 minutes, or until the cupcakes spring back when lightly touched.
Remove from pans and cool on a wire rack.