Soak rolls in cold water. Peel and finely dice the onions. Squeeze the bread roll. Knead minced meat, bread roll, half of the onions, egg and tomato paste. Season with salt and pepper.
Form 8 meatballs from the mixture. Peel, wash and chop the potatoes. Peel carrots and cut into pieces. Peel and halve cucumbers, remove seeds. Cut cucumbers into thick slices. Heat 3 tablespoons of oil in a pan.
Fry the potatoes until golden brown. Add cucumbers, carrots and remaining onions, fry briefly. Add stock, bring to the boil and simmer for about 10 minutes. Heat 2 tablespoons of oil in a second pan.
Fry the meatballs in it at medium heat for about 12 minutes, turning several times. Pour cream into the cucumbers, bring to the boil and thicken with sauce thickener. Season to taste with mustard, salt and pepper. Wash the dill, shake dry and, except for something to garnish, chop and sprinkle over the braised gherkins.
Arrange meatballs and cucumbers on plates. Garnish with dill.