Sauce Method Start by making the sauce, soften the onion, garlic & thyme leaves with the butter in a heavy based pan until soft & translucent. Add the mushrooms & continue cooking until all the juice evaporates. Next, add the stock & Dijon mustard. Reduce until rich & glossy then fold through the crème fraiche. Keep warm whilst you cook the steak strips. Beef Method Preheat a heavy based frying pan until it sizzles when you add a drop of oil. Season the meat with sea salt & a few turns of black pepper just prior to cooking. Sear the meat in the oil, don't overcrowd the cooking base, this is really important so the meat doesn't boil. Cook over high heat turning the steak strips on all sides for 2 to 3 minutes in total. Finish by adding the prepared sauce, grain mustard & chopped parsley, stirring thoroughly then remove immediately from the heat. Serve with dumplings & buttered spinach.