2 x 500 g (1 lb) cartons ready-made fresh mashed potato
50 g (2 oz) dill, roughly chopped
25 g (1 oz) Parmesan cheese, freshly grated
salt and pepper
Place the salmon in a microwave-proof container and pour over 2 tablespoons water. Cover and cook in a microwave oven on high for 3–4 minutes until the fish is opaque and cooked through. Set aside and then flake into large chunks.
Melt the butter in a saucepan, add the flour and cook over a medium heat, stirring, for a few seconds. Remove from the heat and add the milk, a little at a time, stirring between each addition. Then bring to the boil, stirring, until thickened. Remove from the heat and season with salt and pepper.
Add the leeks and peas to the sauce, then gently stir in the salmon. Transfer to a large gratin dish. Place the mashed potato in a large bowl and beat with 2 tablespoons water and two-thirds of the dill until soft and smooth. Spoon over the salmon mixture and scatter over the Parmesan. Place in a preheated oven, 200°C (400°F), Gas Mark 6, for 10 minutes, then transfer to a preheated high grill and cook for 5 minutes until the top is browned. Scatter with the remaining dill.