The mushrooms on top are so simple. So very simple. Everyone seems to get their panties in a bunch over mushrooms and thyme together. Sure, that's good and all, but a bit unoriginal at best. I prefer oregano. So I cooked ~8oz sliced button mushrooms with S+P and ~1T of chopped fresh oregano in about 2T of butter.
A note about mushrooms: any mushroom that is Agaricus Bisporus, which includes button mushrooms, crimini/baby bella, and portabella, will give off a bit of ammonia as the cell structure breaks down. This is especially prevalent in older mushrooms. It's not a big deal at all because the numbers are so small, but it is a good idea to leave your mushrooms uncovered during cooking so the shrooms can breathe.