Cut the beef fillet into strips across the grain and season with salt and pepper. Slice the mushrooms and finely dice the shallots.
Heat the olive oil in a large frying pan over a high heat and sear the beef strips briefly in batches. Take them out and leave to rest briefly so they stay juicy.
Melt the butter in the same pan and fry the mushrooms until golden brown. Add the shallots and fry until soft and fragrant.
Stir in the cream, Dijon mustard and thyme and let the sauce reduce briefly until lightly creamy.
Return the beef strips and their juices to the pan and just warm them gently in the sauce. Don't let it boil any more, so the fillet stays tender.
Serve on warmed plates and spoon the sauce straight over the top.
Good to know
When it needs to be quick but should still taste like a proper meal, this dish is just right. The sauce is creamy, the meat stays tender, and everything is on the table without much effort.
Swaps
Beef fillet → rump steak (similar protein content, usually a little cheaper). Cream → crème fraîche (a little tangier, similarly rich). Butter → ghee (contains only traces of lactose, can be heated to high temperatures). Mushrooms → king oyster mushrooms (more bite, also contain fibre).
Allergens
Contains milk (cream and butter) and mustard. Usually good for children if mildly seasoned; in pregnancy it's fine as long as the beef is cooked right through – leave the strips in the sauce a little longer until no pink remains.
