For the meatballs peel onions and dice 2 finely. Knead minced meat, half onion, mustard, breadcrumbs and milk. Season with salt and pepper and form into about 20 meatballs. Halve 1 onion. Season 2 litres of boiling salted water with onion, bay leaf and juniper and cook the meatballs for about 10 minutes.
Peel the cucumbers, cut them in half lengthwise, remove the seeds and cut the flesh into slices. Remove meatballs from the stock, pour stock through a sieve. Measure out 1 litre of stock, bring to the boil and cook the cucumbers for about 6 minutes. In the meantime peel and wash the potatoes and cook them in boiling salted water for about 20 minutes.
Pour the cucumbers into a sieve, collect the stock. Melt the fat in the pot. Sauté the remaining onion cubes in it until transparent. Stir in flour and sweat briefly. Add approx. 500 ml cucumber stock and milk while stirring. Bring to the boil, let it boil for about 5 minutes, season with salt and pepper. Add capers, gherkins and meatballs to the sauce and heat up.
Parsley wash, dry shake, leaves, except for something to garnish, from the stems pluck and chop finely. Drain potatoes, add parsley and 20 g butter and toss potatoes in the butter and parsley. Arrange potatoes and ragout and garnish with parsley.