Cook the potatoes in boiling water for about 20 minutes. Meanwhile clean broccoli and cauliflower, divide into florets and wash. Cook the cauliflower in boiling salted water for about 8 minutes. After approx. 3 minutes add broccoli and cook. Drain and let drain. Wash the salmon, dab dry and cut into cubes.
Season with salt and pepper. Heat oil in a pan, fry salmon cubes in it and take them out. Drain potatoes, rinse with cold water and peel. Peel and finely dice the shallot. Melt the fat in a pot and sauté the shallot in it. Add flour while stirring and sweat for about 1 minute. Stir in milk and let it simmer for about 5 minutes. Wash the dill, dab dry and chop finely, except for a little bit for garnishing. Stir dill and lemon juice into the sauce. Season to taste with salt, pepper and sugar. Cut the potatoes into slices. Place potatoes, salmon, cauliflower and broccoli in a greased ovenproof dish or 4 small moulds.
Wash the dill, dab dry and chop finely, except for a little bit for garnishing. Stir dill and lemon juice into the sauce. Season to taste with salt, pepper and sugar. Cut the potatoes into slices. Place potatoes, salmon, cauliflower and broccoli in a greased ovenproof dish or 4 small moulds. Pour bèchamel sauce over them. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 12 minutes. Take out and serve garnished with dill