Rub the fillet well with salt, pepper, thyme, rosemary and dill. Cover with aluminum foil and let it soak for about 30 minutes.
Then fry in hot oil on all sides, add butter, onion and sliced mushrooms, briefly toast everything, fill up with a little broth and place in the preheated oven (approx. 220 °).
Fry for about 25 minutes, dousing the broth more often. Then pour in the cream, bring to the boil again and season the sauce with lemon juice, parsley and possibly wine.