1) Boil the potatoes in a sauce pan. Once cooked, drain the water and mash it. Add about 2 tbsp. butter. Season with salt and pepper then set aside.
2) Pre-heat oven to 350F/175C.
3) In a small sauce pan, melt the butter and add the flour to make a rue. Then add the milk and stir it constantly till the sauce thickens. Add salmon fillet, sweet corn, green peas, chives/paraley and season with salt and pepper. Mix it well.
4) Transfer in a oven proof dish then add and spread the mash potato on top. Sprinkle with grated cheese and bake it for 20-25 minutes.
5) Remove from the heat and ready to serve.