Peel and wash the potatoes and cook them in boiling salted water for about 20 minutes. Peel and finely dice the onion. Knead the mince, egg, onion and breadcrumbs. Form small balls from the mixture. Heat the oil and fry the balls for 5-8 minutes until golden brown.
Clean the carrots, leaving a little green, peel and cook in boiling salted water for 8-10 minutes. Drain the potatoes. Warm the milk lukewarm, add it to the potatoes, mash them coarsely and season with nutmeg. Stir the contents of the bag with a whisk into 125 ml cold water, bring to the boil while stirring. Switch off the stove. Cut butter into pieces and fold in well until melted. Stir in mustard and remove from the heat immediately. Drain the carrots. Wash parsley, cut into strips and fold into the mashed potatoes.
Switch off the stove. Cut butter into pieces and fold in well until melted. Stir in mustard and remove from the heat immediately. Drain the carrots. Wash parsley, cut into strips and fold into the mashed potatoes. Arrange the carrots, meatballs, sauce and mashed potatoes