I'm not an expert, but that's a pretty big difference. I don't know whether it will be ruined, but it will certainly be much different than the original!! is it too late to add the yolk also??
Since it's icing, I'm betting you'll be putting it on something else that took time and energy to make. I wouldn't risk it. If you add in both the yolk and the egg white, you'll have too much liquid in the recipe. If you leave out the yolk, you may be missing something important as the yolk and white are quite a bit different. I'm no expert, though. Good luck!
Re: Any bakers????