Heat a large fry pan with a lid and add in the oil. Add in all the vegetables, and cook for a couple of minutes, push the vegetable to the side of the pan and lightly fry the salmon for a couple of minutes, pour in the stock and cover the pan with a lid. Bring the pan to a light simmer and cook for 3 – 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 vegetable with a fork until finely diced.
Break up all the salmon flesh and mix with the vegetables. Whisk the mascarpone with the egg yolks, the egg and season with salt, pepper, lemon zest and parmesan. This should make a slightly thick paste.
Before you start layering the lasagne, put one spoon of fish stock (or keep some of the juice that you get from cooking the fish or make extra vegetable juice for this) into bottom of dish to make the lasagne moist.
Layer lasagne sheets with the vegetable, salmon, mascarpone and keep on doing this till all the mixture is used. Put some vegetable or fish liquid over the top. This lasagna should not be too high, just 3 layers. It should be an 'elegant' not a bulky dish.
Set oven at 200°C and let the lasagne warm through gently for about 12 minutes.