Peel, wash and chop the potatoes. Cook in salted water for about 20 minutes. Stir 125g butter/margarine until creamy. Clean and wash spring onions and chop very finely. Wash the herbs and chop, except for a few for garnishing.
Wash the peppers and cut them into very fine strips and chop them very finely. Mix herbs and paprika with spring onions and butter/margarine. Season with salt and pepper. Stir in breadcrumbs.
Wash the fish fillet and dab dry. Season with salt and pepper. Place in a greased casserole dish. Spread the herb and butter crumbs on top and bake in a preheated oven (electric range: 200°C/circulating air: 175°C/gas: level 3) for 15-20 minutes.
Wash the cucumbers and cut them lengthwise into thin slices with a peeler. Salt lightly and let it steep a little. Mix yoghurt, lemon juice and sugar. Squeeze the cucumbers. Mix with yoghurt dressing.
Season to taste with salt.
Drain the potatoes. Press through with a potato ricer. Add warm milk and 2 tablespoons butter/margarine to the puree. Season to taste with salt and nutmeg. Arrange everything. Garnish with remaining herbs.