The best mushrooms are the Chinese dried ones found in most specialty shops or in the Asian section of your grocery store, but you can use other, including fresh mushrooms, if you don’t find them.
Heat the chicken stock, mushrooms, and chicken breast in a saucepan, until the boling point. Reduce heat, and simmer very gently for 5-6 minutes.
Season to taste and serve.
Substitute 1 cup Chinese dried mushrooms with 4 heads fresh mushrooms, thinly sliced.
Make the broth more interesting adding 4 Tbs dry sherry.