Preheat the oven to 175 ° C top / bottom heat (150 ° C with circulating air).
Wash the beef fillet and pat dry. Rub with the mustard and with salt and black pepper. Then cut the fillet into 3 - 4 cm thick slices and season the cut surfaces lightly with salt and pepper.
Chop the herbs very finely. Melt the butter and mix the herbs with the breadcrumbs, the parmesan and a little salt, pepper and the green peppercorns. Let this breading simmer briefly and then set aside.
Heat the oil in a pan and sear the fillet slices on both sides for a good one and a half minutes. Place the seared steaks side by side in an ovenproof dish and coat with the breading - a good 1 cm thick. Place in the hot oven for about 15 minutes. Then take it out and arrange on plates.
It goes well with rosemary potatoes, gnocchi and green salad.