No, there is no way to reduce the sweetnesses of royal icing. Unfortunately it is the nature of the beast. It consists of sugar, eggs whites, and food coloring. And more unfortunate is it is so sweet, it makes the cookies inedible. Other than biscotti and shortbread, I didn’t even bother with cutout Christmas cookies last year.
A chocolate royal icing will be brown. Since the whole point of using royal icing is to create intricate designs on cookies, a batch of brown royal icing will be very limiting. I suppose you could use it as the top coat.
I don’t think you’ll get any real chocolate flavor to speak of. For chocolate, you would have to mix cocoa powder in with the powdered sugar. If you use real chocolate it would seize upon contact with the water.
But cocoa powder is very hygroscopic. It will absorb the water. To prevent the cocoa powder from turning the royal icing into a thick gooey mass, only a small amount of cocoa powder could be used. And it will probably affect how the icing sets up. I think in the end you would end up with brown icing with very little chocolate flavor.
You can use real chocolate on cookies. That’s what I’m planning for Christmas cookies this year. I think real chocolate is the only alternative to royal icing. I’m pretty sure you can’t produce intricate designs with real chocolate.
I just bought several pounds of dark and white chocolate for decorating cookies this holiday. Since I’m not sure which brand will work best I bought four different brands.
I want to make cookies that are edible. Even though royal icing allows you to be extremely creative, the bottom line is it tastes wretched . It’s not worth it to me to spend so much time and money on a cookie that is going to end up in the trash after one bite.