Add the remaining ingredients except for the butter.
Cook until almost the soft ball stage. (When dropping a little bit into a cup of cold water, it should not disperse - it should stay together, but it still doesn't form a ball).
Add 1 tablespoon butter after removing from cooking.
Leave mixture in the pan and cool in a sink of cold water (approximately 15 minutes).
Use electric mixer and beat until it loses it's glossiness.