Thaw the pollack fillets, rinse under water and pat dry with kitchen paper. Cut out the rest of the remaining central bones and cut the fillets into three parts. Then just roll the fish in flour and then fry on both sides.
Peel the onions and cut into rings. Boil the rings with the other ingredients for the brew in a saucepan for about 15 minutes and let them steep at a low temperature.
Put the fried fillets and the stock in layers in a container and seal. Let the fish stand in the refrigerator for about 3 days.