Preheat the oven to 180°C (360°F/Gas 4).
Bring a large pot of lightly salted water to a boil. Blanch the dry lasagne sheets one at a time for about 1 minute, then drain and lay flat on a clean kitchen towel to dry.
Make the ricotta sauce by blending the ricotta with a splash of milk or water until smooth and creamy; season with salt, white pepper and a pinch of nutmeg. Add more liquid if needed for a spreadable consistency.
Heat a large skillet over medium-low heat and add a glug of olive oil. Sauté the crushed garlic and chopped chili briefly, then add the sliced leek and cook gently until softened.
Add the spinach and kale to the skillet, cover and cook 2–3 minutes. Uncover and continue to sauté until the greens are wilted and any excess moisture has mostly evaporated; add a splash of water if needed.
Halfway through cooking the greens, add the cubed salmon to the skillet and cook until the salmon turns pale pink and is just cooked through. Season with salt, white pepper, lemon zest and a pinch of nutmeg.
Lightly oil the bottom of a large ovenproof baking dish. Spread a thin layer of the ricotta sauce over the base.
Assemble the lasagna: add a layer of blanched lasagne sheets, spread a portion of the cooked salmon and greens over them, sprinkle half of the chopped chives and parsley, and spoon more ricotta sauce on top. Repeat to create a second layer.
Top the final layer of pasta with the remaining ricotta sauce and grate the Parmesan evenly over the surface.
Bake in the preheated oven for 20–25 minutes, or until the top is golden and crisp. Let rest a few minutes before slicing and serving.
