Tibetan Mushroom Barley Soup

This is an extremely simple, yet tasty, recipe. Use pot barley if you can find it, but pearl barley will do (just don't cook it quite as long). Using yak butter would make it truly authentic, but good luck finding it...

2 TB butter (or margarine)
2 cups assorted wild mushrooms (shiitake, oyster, crimini, or whatever you like)
1/4 cup barley
4 cups vegetable stock
1 TB soy sauce
salt, pepper to taste

Saute mushrooms in butter over medium heat until softened. Add barley and stock and cover. Simmer for 1 hour, until barley is done, and add soy sauce. Add salt and pepper to taste and serve.