For the meatballs, peel and finely dice the onion. Heat 1 tablespoon butter in a coated pan. Sauté the onion until transparent. Knead minced meat, onion, egg, breadcrumbs and mustard. Season with approx. 1 tsp salt and a little pepper.
Form approx. 30 dumplings from the mixture with moistened hands.
In a wide saucepan, bring 2 litres of water, peppercorns, bay leaf and lemon juice to the boil. Stir in broth. Add the meatballs to the stock and simmer covered over a low heat for about 15 minutes.
In the meantime, peel and wash the potatoes, cover and cook in salted water for about 20 minutes. Lift the finished meatballs out of the stock with a skimmer. Pour stock through a fine sieve and measure 1/2 l.
For the sauce, heat 3 tablespoons of butter in a saucepan. Sprinkle with flour and sauté for about 1 minute, stirring continuously. Stir in 1/2 l stock and cream. Bring to the boil while stirring, simmer for 5-10 minutes. Season to taste with salt and pepper.
Add meatballs to the sauce and heat. Wash parsley, shake dry, pluck off leaves and chop finely. Drain the potatoes, arrange with dumplings and sauce. Sprinkle parsley on top.