Remove the crusts from the bread and cut into small cubes. Put the bread cubes on a baking tray lined with baking paper. Bake in a preheated oven (electric cooker: 150 °C/ convection oven: 125 °C/ gas: see manufacturer) for approx. 15 minutes
In the meantime, peel the onion and carrot. Finely dice both. Heat 1 tablespoon of oil in a frying pan. Fry the diced vegetables over a low heat for 2-3 minutes while stirring. Deglaze with vinegar and white wine, bring to the boil and simmer for about 5 minutes. Add cream and mustard and stir in. Remove from the stove. Remove bread cubes from the oven and let them cool down. Peel, wash and coarsely dice the potatoes and cook in boiling salted water for 15-20 minutes.
Meanwhile wash the meat, dab dry and season with salt and pepper. Heat 2 tablespoons of oil in a large frying pan. Fry the meat in it in 2 portions on each side for approx. 3 minutes, remove, wrap in foil and let it rest for approx. 10 minutes. Heat milk and butter in a saucepan. Drain the potatoes and press them through the potato press into the hot milk. Stir briefly, season to taste with salt and nutmeg
Heat the sauce again. Season to taste with salt and pepper. Arrange entrecotes with sauce on plates. Sprinkle with bread cubes. Add mashed potatoes