Our beloved Pat Llewellyn is convinced that only the Welsh cook salmon in red wine. She may be right. Certainly the renowned Lady Llanover did. It adds a richness to the fish that is quite unique.
Work 25g/1oz of the butter with the flour into a paste (beurre manié) and set aside. Fry the onion and mushrooms in the remaining butter. When soft, add the garlic and rosemary. Pour the fri