Acidify the zander fillets with lemon juice and salt them. Mix flour with chopped parsley and roll the fish fillets in it. Heat a mixture of butter and oil in a pan and fry the fillets first on the flesh side, then on the skin side.
For the saffron-ginger sauce, finely chop the shallots, peel and chop the celery. Heat butter in a pan and roast the shallots until golden. Add the diced celery and ginger and fry. Deglaze with white port and wine and pour in soup. Simmer for 5 minutes, then stir in the cream. Add the saffron threads to the sauce and let it boil down a bit more. Bind the saffron-ginger sauce with some ice-cold butter flakes – the sauce must not boil anymore! Season to taste with a squeeze of lemon juice, salt and pepper.
Serve the pike-perch fillets with the saffron-ginger sauce.