--That's a small tin of mushrooms, not one of those ones you could make an entire meal out of.--
Microwave spinach until not frozen. Cook ramen without adding seasoning. Drain until only about 1/4 inch of water remains. Tilt bowl so that seasoning can be mixed directly into water. Mix in spinach and mushrooms. Put cheese on top.
This can be made impress-your-girlfriend awesome by using sliced portobello mushrooms, instead of tinned mushrooms, and adding 1/3 can of cream of mushroom soup.