Put the milk in a pan on low heat and warm it (not boil). Start by making bechamelle by melting the butter in a tall pan, add the flour (little bit at the time).
On low heat add the milk a paddle at the time and mix well with the flour every time.
Eventually the mixture will start to get more liquid. To finish we are aiming for this consistency (see video below)
Leave to cook on very low heat for 10min and then remove from fire. To avoid it making a thick crust cover with cling film directly on the bechamelle.
Make the pesto. You can make this ahead of time and leave it in a jar in the fridge. In a small pan bring water to boil, add the pistachios and cook for a couple of minutes. Remove them from water
Now that the skin softened remove all the skin and add the pistachios skinless in a mixer. Add the Parmesan, basil, salt, oil and a dash of water. Mix well and add oil/water as needed. Remove from mixer
In a large pan cook for a couple of minutes the prawns with a dash of brandy. Remove from the fire.
In an oven proof dish, add a thin layer of bechamelle to ensure that the lasagne won’t stick to the bottom. Lay down the lasagne sheet, cover with bechamelle, add pieces of salmon, the prawns and dashes of pesto and a sprinkle of Parmesan. Repeat 3/4 layers
Finish with a layer of bechamelle and cover with the grounded pistachios for decoration.
Cover with a slightly wet piece of baking paper on top of the dish. Cook on 180 degrees for 20 minutes. Finish with 5 min under the grill to make it golden
