Wash the salmon, dab dry and cut into large cubes. Season with 2 tablespoons lemon juice and salt. Clean the savoy cabbage, cut leaves from the stalk, wash and cut out thick leaf veins.
Blanch the leaves in boiling salted water for about 2 minutes, drain and leave to drain. Heat the fat in a pot, dust with flour and sauté while stirring. Gradually add broth and milk.
Add lemon zest. Simmer for 5 minutes, stirring frequently. Season to taste with 2 tablespoons of lemon juice, salt and pepper. Put some sauce in a greased casserole dish. Layer 3 lasagne plates, half of the salmon and savoy cabbage on top.
Cover with sauce, add 3 lasagne dishes, the rest salmon and savoy cabbage. Pour in the sauce, lasagne dishes and the rest of the sauce. Cut the mozzarella into sticks and sprinkle over the top. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 40-45 minutes.
Garnish with dill and lemon.