Clean and wash the spinach. Peel onion and garlic, dice finely and fry in 1 tablespoon of hot fat. Add the spinach dripping wet, let it collapse. Season with salt, pepper and nutmeg. Drain very well on a sieve. Cook the pasta in boiling salted water for about 8 minutes until al dente
Heat 40 g butter. Add flour and sweat while stirring. Deglaze with approx. 3/8 l water, milk and Noilly Prat, stir in broth and bring to the boil. Simmer for about 5 minutes. Season the sauce with salt and pepper
Drain the pasta, let it drain. Wash the fish, pat dry and sprinkle with lemon juice
Grate cheese, mix. Put approx. 1/3 of the sauce into a greased casserole dish (approx. 2 1/2 l capacity). Spread half of the pasta and half of the spinach on each. Sprinkle with about 1/3 cheese. Pour approx. 1/3 of the sauce over it. Place salmon on top and season with salt and pepper. Layer the rest of the spinach, about 1/3 cheese and the remaining noodles. Pour the rest of the sauce over it and sprinkle with the rest of the cheese
Bake in a hot oven (electric oven: 200 °C/circulating air: 175 °C/gas: level 3) for 40-45 minutes. If necessary, cover with parchment paper for the last 10 minutes