Pork fillet with a steel or wooden spoon handle, pierce lengthwise, in the middle. Place the truffle liver sausage in a piping bag with a large perforated spout. Pipe the sausage into the fillet.
Season meat with salt and pepper. Clean and wash the soup greens. Finely dice carrot and celery, cut leek into thin rings. Peel onion and also cut into small cubes. Heat clarified butter in a pan, fry vegetables and onions in it.
Remove and fry the fillet thoroughly all around. Add 1/4 litre water, bring to the boil and stir in the sauce powder. Add vegetables and bring to the boil again briefly. Cook pork fillet with the vegetables in the preheated oven (electric cooker: 150°C/ gas: level 1) for 20-25 minutes.
In the meantime, clean and wash the cauliflower and asparagus. Divide the cauliflower into florets. Cook vegetables separately in boiling salted water for 8-10 minutes, drain. Froth butter in a pot and pour over the vegetables.
Season with salt and pepper. Cut the fillet open and arrange on a plate together with the vegetables. Pour some sauce over the meat and serve garnished with parsley. Add the rest of the sauce extra.