Peel onion and chop very finely. Knead 50 g butter and onion. Season with pepper. Form into a roll, wrap in aluminium foil and chill. Grate cheese finely. Wash and peel the asparagus and cut off the woody ends
Peel the potatoes and cook in boiling salted water for about 25 minutes. Drain, add 25 g butter, toss well covered. Place on a baking tray, leave some space on one side of the baking tray for the fillets. Sprinkle the potatoes with cheese and bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 20 minutes
Wash the meat and dab dry. Heat the oil in a pan and fry the meat thoroughly all around. Season with salt and pepper, remove from the pan and place on a baking tray and bake for 10-12 minutes. Meanwhile, cook the asparagus in boiling salted water with 1 tsp. sugar for 12-15 minutes.
Wash the herbs, shake dry and chop finely. Cut onion butter into slices. Take the meat out of the oven and let it rest for a while. Lift the asparagus out of the water and let it drip off. Foam 50 g butter in a small pot. Add herbs
Arrange meat with onion butter, potatoes and asparagus sprinkled with herb butter on plates