Wash the fish, dab dry and cut into pieces. Sprinkle with lemon juice and season with salt and pepper. Peel and finely chop the onion. Peel carrot and cut into pieces.
Clean, wash and slice the leek. Coarsely dice the gherkins. Heat the oil in a pan and fry the onion in it. Add fish and fry for about 5 minutes. Add carrots, leek and gherkins, steam briefly and season with salt and pepper.
Deglaze with stock and cream, bring to the boil and cook over a low heat for 8-10 minutes. In the meantime put rice balls in a pot with cold water. Bring to the boil and cook over low heat for about 10 minutes.
Turn over occasionally. Add the sauce thickener to the fish goulash while stirring, bring to the boil again and season to taste. Wash the rocket, dab dry and cut into strips, except for a little garnish.
Wash the dill, dab dry and cut finely. Add both to the fish goulash and fold in. Take rice balls out of the water and let them drain. Remove the cooking bag and arrange the rice balls with the fish goulash on plates.
Serve garnished with remaining rocket.