Soak rolls in cold water. Clean and wash the soup greens. Dice celery, cut carrots and leek into slices. Pre-cook the soup greens in boiling salted water for 4-5 minutes, pour onto a sieve and drain. Peel and chop the onion. Squeeze the bread roll well and knead it together with the mince, egg, onion, mustard, salt and pepper to a smooth mass.
Mix approx. 2/3 of the soup vegetables into the minced mass and form a roast. Place the meatloaf in a roasting pan and spread the remaining soup vegetables around it. Add 4-5 tablespoons of water. Roast in the preheated oven (electric cooker: 200°C/ gas: level 3) for about 45 minutes. Add some water if necessary. In the meantime, wash the potatoes and cook in plenty of boiling water for about 20 minutes. Heat the fat in a pot and sauté the flour in it. Add stock and milk while stirring, bring to the boil and simmer for about 5 minutes. Season béchamel sauce with salt, pepper and nutmeg. Wash parsley, dab dry and chop finely, except for a little bit for garnishing. Add parsley to the sauce. Drain the potatoes, rinse with cold water and peel.
Add stock and milk while stirring, bring to the boil and simmer for about 5 minutes. Season béchamel sauce with salt, pepper and nutmeg. Wash parsley, dab dry and chop finely, except for a little bit for garnishing. Add parsley to the sauce. Drain the potatoes, rinse with cold water and peel. Depending on the size, cut the potatoes in half or leave them whole and also add them to the hot sauce. Leave meatloaf to rest for 5-10 minutes, then cut open and arrange on a plate with the vegetables and béchamel potatoes that have been braised with the meatloaf. Serve garnished with parsley