Vegetable soup with kletski from pikeperch

Ingredients for 4:

0.25 lb toasted bread
4 tbsp heavy whipping cream
0.5 lb pikeperch fillets, de-boned and de-skinned
1 egg
0.5 lb sour cream
0.5 tbsp thinly sliced dill greens
Salt and pepper on taste
1/3 lb champignons
0.25 lb celery stalks
3 medium onions
1 tbsp olive oil
0.5 tbsp thinly sliced sorrel
1 l vegetable broth
Baking paper

Method:

To make the "kletski":

Pour whipping cream evenly over the bread.
Make a puree from the fish fillet, and place it in a freezer for 15 minutes.
Mix the fish puree with egg, sour cream, dill, salt and pepper. Blend for about 10 minutes.
Add the soaked bread, and blend together for 2 minutes more.
Cut baking paper in the future kletski-size squares. (note, kletski are essentially fish meatballs)
Make the kletski with 2 teaspoons, and place each on a separate piece of paper.

Cut the mushrooms, onions, and celery into small cubes, and simmer with ½ cup boiling water for about 10 minutes. Set aside.

Bring the vegetable broth to boil in a wide saucepan, place the kletski on the paper pieces in the saucepan, and when they cease sticking to paper, carefully remove paper pieces.

Turn heating to low. The broth has to be very hot but not boiling, let simmer for 15 minutes.
Then, add the simmered vegetables and mushrooms with their broth, and continue to simmer with low heating for 5 minutes.
Then, place the kletski in serving bowls, pour the broth with vegetables and mushrooms over them, sprinkle with sorrel, and serve with a sour cream.