Melt the butter in a frying pan on medium heat and add the thyme for about a minute. Then Add the Onion and saute for about 2-3 mins. add the water and let it slowly cook the onion until softend but only sligtly browned - You want to keep this sauce as white as possible.

Once most of the liquid had gone add remove the thyme and add the mushrooms and again slowly cook for about 4-5 mins until mushrooms have cooked and the liquid has almost gone. spinkle in 2 tsp of AP flour and lightly stir to coat everything and so no lumps.

Cook for about 2 mins and then add the stock for 1 min and then the cream. You can add a little more water if the sauce it too thick but stir continuously. Season to Taste - I love lots of Black pepper.