radearling - It has been pointed out to me that I may have sounded a bit harsh.
I'm not retracting what I said, the time to ask questions is before you do something irrevocable (AKA screw the pooch), but sorry if you found the way I said it offensive, I will try to be a bit more gentle next time.
There is plenty of good information out there on malts (and every other aspect of brewing). If you are planning a new beer or using an ingredient you aren't familiar with, it's in your interest to do a bit of research. In this case look at the Gladfield website, the recommended up to 15% should have given warning that 55% might be a bit on the high side.
If you were looking at a replacement for Weyermann Chocolate Wheat Malt, a visit to their website will say that its used up to 5%
You could even start a thread asking for suggestions (see one circulating on a first dark beer recipe).
As it stands I doubt the brew can be saved, adding more of anything wont help, about the only thing you could do is dilute it with other beer (comes to nearly 100L to get the roast down to something reasonable), or just tip it and learn from the mistake.
If you need help, ask, I and doubtless many others here will be happy to help.
Mark