Grease a flat, rectangular shape, preheat the oven to 200 degrees (gas mark 4).
Place the defrosted pollack fillets in the dish.
Beat the softened butter until foamy, stir in the chopped onions and herbs. Add breadcrumbs, salt and pepper. The mass should be nice and crumbly and no longer runny.
Spread the mixture over the fish fillets and place in the oven for about 30 minutes until the crust is golden yellow and the fish is cooked through.
It goes well with boiled potatoes and cucumber salad.