Peel the onion and chop it roughly. Melt the butter in a casserole and add the onion. Leave it to cook on a moderate heat until soft but not coloured. Add the beef to the onion, thyme, leave it to colour lightly, during 5 minutes.
Sprinkle with the flour and stir to combine , add the white wine and increase the heat during 3/4 minutes. Tip into the casserole with the water (the water must recover slightly the pieces of meat ).
Check the seasoning bring to the boil and simmer for 5 minutes then stir into the casserole covert to a moderate heat, stirring occasionally.
In a bowl, soak the dried porcini mushrooms in hot water for about 30 minutes. Drain and add in the casserole 20 minutes before the end of the cooking time.
You could serve this stew with rice, pasta, polenta or millet seeds.