Prepare the mashed potatoes as usual (or use the rest), it should be firm rather than too runny. Put in a buttered baking dish.
Cut the tomatoes into slices and spread over the puree like a roof tile. Sprinkle with salt.
Rinse the fish fillets, dry them with kitchen paper, place them next to each other on the tomatoes.
Squeeze the lemon. Put the juice together with coarsely chopped onions, broken crackers, creme fraiche, salt, cayenne pepper, basil, parsley and oil in a tall container and puree to a cream with the hand blender. Spread these evenly on the fish fillets so that they are completely covered.
Baked in the oven for about 30 minutes at 175 °.
Tip:
If you don`t have a hand blender, you can finely crumble the crispbread in the freezer bag with a rolling pin, the onions are possible. finely chopped and then mixed with the other ingredients.