Heat a large fry pan with a lid and add the oil and then add in all the vegetables and cook for a couple of minutes and then push the vegetables to the side of the pan and lightly fry the salmon a a couple of minutes and then pour in the stock and cover the pan with a lid and bring the pan to a light simmer and cook for 3 to 4 minutes or until the salmon is just cooked through.
Remove the salmon onto a plate and let the vegetables continue cooking until they are very soft and most of the liquid has been absorbed, smash the vegetables with a fork until finely diced.
Break up all the salmon flesh and mix with the vegetables.
Whisk the mascarpone cheese with the egg yolks, the egg and season well with salt and pepper and then add the lemon zest and parmesan - this should make a slightly thick paste.
Before you start layering the lasagna, put one spoon of the fish stock or keep some of the juice that you get from cooking the fish or make extra vegetable juice for this, into the bottom of the dish to make the lasagna moist.
Layer the lasagna sheets (you may need to break these to fit the dish) with the vegetables, salmon and mascarpone mix and keep on doing this till all the mixture in used, put some vegetable of fish liquid over the top.
This lasagna should not be too high, just 3 layers, it should be an elegant not a bulky dish.
Sprinkle extra parmesan cheese on the top.
Place dish in the oven and bake lasagna to warm through about 12 to 15 minutes.