I recently bought some mushrooms from the farmers market and have kept them in a brown paper bag on top of the fridge. 4 days later, they have started to have a slight odor between a mixture of dirt and dogs droppings. I suspect I have stored the mushrooms improperly, so it begs the question: What's the best way to store fresh mushrooms?
Mushrooms should be stored in the refrigerator in a breathable container. A paper bag works great. Mushrooms stored in this manner should last at least 4-5 days.
For the record, the top of the fridge is one of the worst places to store foods. Depending on the model it can actually be a few degrees higher than ambient temperature, thus accelerating spoilage.