Here is the mushroom soy sauce I mentioned in the previous post. Well, it's one version. This one is by Lee Kum Kee, not the best manufacturer by a long shot. Flavoured with 草菇 (cǎo gū - literally 'grass mushrooms') known in English as 'straw mushrooms'.
Their version uses straw mushrooms. Basically this is just another dark soy sauce flavoured with the 'shrooms. A tiny amount in this variety - it's the last listed ingredient.
Ingredients: in order of amount
Water, salt, defatted soy, wheat, wheat flour, caramel, MSG, white sugar, potassium sorbate, straw mushroom. Industrial food.
Better versions use greater amounts of mushroom, normally shiitake. My hunt shall continue.