1. Preheat the oven to 210°C (410°F).
Thaw the spinach well in advance. Preheat the oven to 210°C (410°F).
2. Grease a rectangular or square baking dish with butter, then layer lasagna sheets, salmon, spinach, and a sprinkle of Parmesan cheese. Repeat the process until all the ingredients are used.
3. Pour the previously seasoned heavy cream over the lasagna.
4. Sprinkle some more Parmesan cheese on top and bake in a hot oven for 25 minutes.