Mix the thyme and pepper with the oil. Rub the beef fillet vigorously with it and marinate for 1 hour.
Then put the meat together with the remaining marinade in a strongly heated roaster and sear it all over. Then fry for another 5 minutes over medium heat. Salt and place in the preheated oven at 120 ° C for about 15 minutes. Remove the meat and wrap it in aluminum foil and let it rest for another 10 minutes.
At the same time, cook the Brussels sprouts in salted water with the addition of nutmeg until they are al dente.
Put the crème fraîche in the roasting pan with the roasting liquid, bring to the boil and season with salt and pepper.
To serve, the meat is cut into thin slices, placed on a saucepan and served with the drained Brussels sprouts.
Boiled potatoes, French fries, croquettes or dumplings can be served as an accompaniment. Both a `cool blond` and a semi-dry red country wine are suitable as a drink.