Wash the fish, dab dry with kitchen paper. Sprinkle fillets with lemon juice and salt. Clean, wash and cut the celery into pieces. Wash, clean and halve the mushrooms. Peel and finely chop the onion. Put rice in 200 ml boiling salted water, cover and let it swell for about 20 minutes at low heat.
Meanwhile put 250 ml cold water into a small pot, stir in sauce powder with a whisk. Bring to the boil while stirring and let it boil over low heat for 1 minute. Heat 1 tablespoon of oil in a frying pan and sauté the onion, celery and mushrooms. Pour sauce over it and let it simmer at low heat for 3-4 minutes. Keep the sauce warm afterwards. Whisk the egg with a fork. Mix breadcrumbs and dried parsley. Heat the remaining oil in a frying pan. Turn the fish first in the egg and then in breadcrumbs. Place in the pan and fry over medium heat for 3-4 minutes on each side. In the meantime, wash parsley, dab dry and chop finely. Put rice in a bowl and dust with paprika.
Mix breadcrumbs and dried parsley. Heat the remaining oil in a frying pan. Turn the fish first in the egg and then in breadcrumbs. Place in the pan and fry over medium heat for 3-4 minutes on each side. In the meantime, wash parsley, dab dry and chop finely. Put rice in a bowl and dust with paprika. Arrange the fish and sauce on a plate, sprinkled with parsley. Serve garnished with parsley as desired