Your chocolate seized, and there are ways to fix it. But first, you should know that it was caused by even a tiny amount of water or steam (or any other liquid. Oddly enough, the fix is to add more liquid. Renowned food scientist and cookbook author Shirley Corriher uses the rule of thumb that for every 2 ounces of chocolate, you must have a minimum of 1 tablespoon of liquid. Liquid might include butter (butter contains about 18% water), cream, corn syrup, alcohol, or water.
Also, you can melt the chocolate with the butter or cream for better results. For more tips, watch our how-to video on melting chocolate.