Peel the potatoes, clean and wash the celery and cut into slices. Bring both to the boil in 1/4 l water with broth, cover and steam for approx. 10 minutes
Clean, wash and cut the spring onions into rings. Wash tomatoes, cut into slices. Add both to the potatoes. Season everything with salt and pepper
Stir half the crème fraîche into the vegetables and season to taste. Pour into a large greased casserole
Rinse the fish, pat dry and dice roughly. Salt and turn in flour. Fry briefly in hot oil. Spread on the vegetables. Mix the rest of the crème fraîche and mustard and pour over the fish. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/gas: level 3) for 15-20 minutes
The vegetable and fish casserole covers about 3/4 of the daily requirement of potassium. In addition, it provides iodine, phosphorus, iron and calcium