Peel and wash the potatoes and cook them in boiling salted water for 25 minutes. Soak rolls in cold water. Peel and finely chop the onion. Knead minced meat, egg, onion and squeezed out roll.
Season with salt, pepper and paprika. Drain the potatoes and mash them finely. Stir in milk and 30 g fat. Wash and chop the parsley, except for a little bit for garnishing. Stir parsley and roasted onions into the puree and let it cool down.
Roll out minced meat on cling film to a plate (30x30 cm). Spread mashed potatoes on top and roll up with the help of the foil. Place the minced meat roll on the fat pan of the oven with the seam side down.
Roast in the preheated oven (electric cooker: 175 °C/ gas: level 2) for 1 1/4 hours. In the meantime, clean, wash and cut leek and carrots into pieces. Heat the remaining fat in a pot.
Sauté the leek in it. Add stock and cook for 5 minutes. Add cream, bring to the boil and thicken with sauce thickener. Bring to the boil again. Season to taste with salt and pepper. Arrange the chopped roll with the vegetables on a plate.
Garnish with parsley.