Ingredients for 4 servings: 600 g veal or beef liver, 3 large onions, 3 tbsp flour, 3 tbsp clarified butter or oil, salt and pepper. For the sauce: 150 ml beef stock, 1 tsp mustard, 1 tsp butter, and a splash of apple cider vinegar, if desired. For the mashed potatoes: 900 g floury potatoes, 200 ml milk, 40 g butter, salt, and nutmeg.
Peel the potatoes, cut them into small pieces, and boil them in salted water for about 20 minutes until tender. Meanwhile, slice the onions into thin rings and sauté them slowly in a little clarified butter over medium heat until golden brown. Remove from the pan and keep warm.
Pat the liver dry, lightly coat it in flour, and shake off any excess. Fry it in a hot pan for about 2–3 minutes on each side, depending on its thickness. Season with salt and pepper and keep warm.
Peel the potatoes, cut them into small pieces, and boil them in salted water for about 20 minutes until tender. Deglaze the pan with the broth, stir in the mustard, and simmer the sauce for 2–3 minutes. Finally, stir in the butter and, if desired, a splash of apple cider vinegar.
Drain the potatoes and let them steam briefly. Add warm milk and butter, mash until smooth, and season with salt and nutmeg.