1. Combine the butter and the garlic, mix well.
2. Shape into a roll, wrap in cling film and freeze.

To Prepare Mushroom Sauce:

1. Heat the butter in a pan.
2. Add onions and mushrooms, stir and cook until onion is soft.
3. Add the flour, cook stirring for one min.
4. Remove from heat and gradually add the stock, stirring continuously.
5. Place the pan back on the fire.
6. Stir in the egg yolks, chives and lemon juice and cook until mixture boils and thickens.

1. Melt the butter in a pan, do not allow it to brown.
2. Stir in the rosemary and parsley, then season with lemon juice, salt and pepper. Remove from fire.
3. Cover the fish with the flavoured butter and grill till done.
4. Serve with mushroom sauce.