Melt 100 g/4 oz of the butter in a frying pan.
Add the mushrooms and fry quickly until just tender.
Stir in the garlic, salt and freshly ground black pepper.
Divide between 6 small ovenproof dishes.
Divide the remaining butter into 6 portions and place one in each dish.
Top with the cheese.
Bake in a preheated moderately hot oven (200°C/400°F, Gas Mark 6) for 15 minutes.