I did these for breakfast this morning after a party at a friend's house, they're lovely on toast, with bacon, or just by the spoonful on last night's baked potatoes.
Tear mushrooms in pieces and cook in a fair bit of butter. Add as much garlic as you can find or stand. This morning we also had black pepper, thyme, paprika and a glass of leftover white wine. Cook on a medium heat until the liquid comes out of the mushrooms and evaporates, and they start to fry off brown in the butter. Add creme fraiche, heat through and serve. If you leave them sitting on a slow heat, even a hot tray, the cream will slowly absorb into them and split with the butter, leaving lovely garlicky oozy fatty juices. If you don't like that, stir in some more cream and rewarm, it'll come back together again for a bit. You need loads of mushrooms, I used two 750gm boxes this morning, to a large tub of cream, and that only served about a dozen people. They cook down to nothing.
You can also add brandy, concentrated liquid stock (beef or chicken), curry powder or paste if you're that way inclined, or finely chopped fresh parsley. But I don't usually add salt other than what's in the stock.