Put a little butter and olive oil in a saucepan and add the mushrooms, onion, garlic, thyme, rosemary, nutmeg and black pepper. Cook over a gentle heat for about 20 minutes, stir occasionally. The mushrooms will give out lots of liquid at first but by the end of the cooking time the pan should be fairly dry. Take off the heat and leave to cool.
Put the mushroom mixture and cream cheese in a food processor. Blend until smooth.
Line 2 or three ramekins with cling film (optional). Spoon the pate into the ramekins and flatten the top with a spoon.
Melt the butter in the microwave or in a small pan. Let cool slightly then pour on top of the paté to seal it in. When the butter has fully cooled and hardened, put the ramekins in the fridge to store until ready to serve.
Nutritional information is approximate and a guideline only.