Slice the mushrooms into thin slices.
It will look like a big heap of mushrooms but they reduce in size to about a quarter of that once cooked.
Melt butter in a frying pan and fry the mushrooms for about 10-15 minutes, until golden brown.
When mushrooms are almost ready, season with salt and pepper and add garlic if using.
Add crème fraîche to the pan and mix well until all mushrooms are covered.
Put mushrooms into two individual ramekins and top with grated cheese.