Peel, wash and chop the potatoes. Peel the celery and cut into equally large pieces. Cook potatoes and celery in salted water for about 20 minutes until soft.
Clean the salad, wash and shake dry. Roast the pine nuts in a pan without fat, remove. Clean, clean and halve the mushrooms. Heat 3 tablespoons of oil in a pan and fry the mushrooms.
Season with salt and pepper. Mix vinegar, mustard, salt and pepper. Fold in olive oil in portions.
Knead the flour and 2 tablespoons of butter, divide into small flakes and chill. Dab meat dry and cut into 4 medallions of equal size. Season with salt. Heat 2 tablespoons of oil in a frying pan. Fry the medallions in it vigorously from each side for 3-4 minutes.
Remove from the pan and wrap in aluminium foil. Let it rest for about 5 minutes.
Add cream and beef stock to the frying pan and bring to the boil. Gradually fold in flour butter until the sauce thickens. Heat milk and 30 g butter in a small pot. Drain potatoes and celery and mash them coarsely.
Add the milk-butter mixture. Season with salt and nutmeg. Mix salad, pine nuts and vinaigrette. Garnish plate with balsamic cream if necessary. Arrange beef fillet, salad, mashed potatoes and mushrooms on the plates.
Drizzle with gravy.