Make 1 litre of white sauce, not too thick, and add the parsley, finely chopped. Once cooked, chop the tomatoes and salmon in small pieces.

In a small/medium oven dish put a couple of ladles of white sauce on the bottom. On a lasagna sheet add a spoon of white sauce some tomato and a bit of salmon but don't overfill it. Cut the lasagna sheet in half and roll. Lie the rolled lasagna facing upwards.

When all the lasagna is done spread evenly the leftover white sauce and add a sprinkling of cheese and a couple of knobs of butter. Cook for 20 min at 180 degrees.