Clean and clean the mushrooms and, depending on the size, possibly halve them. Peel onion and cut into fine slices. Peel garlic and chop finely.
Heat the oil in a wide saucepan. Sauté the mushrooms in it while turning them. Add onion and garlic and fry briefly. Season with salt and pepper. Remove the mushrooms and put them aside.
Add 900 ml water and cream to the pot. Add spaghetti, bring to the boil, stir in broth, cover and cook over medium heat for 10 minutes. Stir occasionally so that the spaghetti absorbs liquid evenly and does not stick.
Meanwhile, wash the lemon, rub dry and grate the peel. Pluck the thyme leaves from the stalks. Add thyme, spinach and mushrooms to the spaghetti and bring to the boil again. Season to taste with lemon juice, salt and pepper. Pluck the salmon and fold in just before serving.