Wash the potatoes and cook for about 20 minutes. Then quench, peel and let cool. Clean and wash the spinach. Wash fish, dab dry and sprinkle with lemon juice
Peel and finely dice the onions and garlic. Fry in hot oil. Add spinach and let it collapse (steam frozen spinach according to package instructions). Season with salt and pepper
Sauté the flour in 2 tbsp. hot butter. Stir in 1/2 l water, milk, wine and stock. Bring to the boil, simmer a little and season to taste
Cut the potatoes into slices. Layer with spinach in a greased casserole dish (approx. 30 cm long). Season salmon with salt and pepper and place on top. Pour sauce over it. Crumble the bread. Add 1 tbsp. butter in flakes. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for about 30 minutes
It is best to buy salmon only on the day of preparation. Or keep it covered in the refrigerator for max. 1 day. If you take frozen salmon, let it thaw gently in the refrigerator in a covered sieve