Break apart or slice any larger mushrooms so they are all roughly the same size. In a large frying pan, melt the butter then add the garlic followed by the mushrooms. Fry until golden (about 5 minutes depending on the size of the mushrooms). Be sure not to overcrowd the pan or the mushrooms won't colour.
Add the cannellini beans, crème fraîche and fresh thyme and warm gently for a couple of minutes.
To serve, top the buttered toast with the mushrooms and bean mixture. Garnish with a little more fresh thyme and serve immediately.
Cook's tip: if you love garlic, rub the sliced bread with the cut side of a halved raw garlic clove just after toasting.