Spoon and spread a little of the sauce over the base of a 9 x 13 ovenproof dish and arrange a layer of lasagna sheets, overlapping, on top. Scatter over a third of the salmon and asparagus, followed by some of the white sauce. Add another layer of lasagna, another layer of asparagus and salmon, and another layer of sauce. Continue to layer up, making sure you finish the top layer with pasta topped with sauce. Sprinkle the remaining chives and Parmesan on top.