Soak the tarhana in the water for three or four hours. Separately soak the beans in water, preferably overnight. Drain beans and cook in a pot in water until tender and soft but not mushy. In another pot bring the tarhana to a simmer, stirring with a wooden spoon to avoid clumps. Cook on a low flame, 90 minutes. Drain the beans and add them to the Tarhana. Add the butter and enjoy your soup while warm.