Agree with all that. The mushrooms often served in caffs or restaurants are all too often grey, thick, rubbery unseasoned abominations sitting in a little pool of rather nasty liquid. I like mine sliced thin, or hacked into smallish chunks, well seasoned and sautéed in hot butter or (as you say) bacon fat. A slice of bread then fried in the fat is very good. I use dried porcini soaking water and the finely-chopped porcini in casseroles and pot roasts, but I never use ordinary mushrooms for that, and I honestly can't see the point of button mushrooms. It's very disappointing when a stack of mushrooms I'm frying almost disappears in a pool of sludge in the frying pan. I've taken to buying the organic ones from Sainsbury's which never seem to do that.