1) In a medium-sized dish, melt the butter in the microwave power full, for 1 minute.
2) Stir in the garlic, lemon juice and black pepper, microwave for another 1 minute.
3) Stir in the mushrooms, until thoroughly coated in the butter.
4) Allow to marinate for several hours, then cover and microwave for 5 minutes.
5) Serve the Mushrooms in Garlic Butter, immediately or cold along with wholemeal bread pieces.