Pre-heat the oven to '190 C, 375F, Gas mark 5.
Drain the can of salmon and reserve the juice. Set aside.
Melt the butter in a pan and cook the leeks and pepper until soft.
Add the sweet corn and flour, mix well. Cook for 1 minute.
Blend the salmon juice into the vegetables and flour. Mix well then gradually add the milk, beating to make a smooth sauce.
Flake the salmon into the vegetables and season to taste.
Mash together the potatoes and cheese until smooth.
Put the salmon into an ovenproof dish and spread the chosen sauce over this.
Pipe or spoon the potato over and bake for 30 minutes.
Serve with peas, sweet corn and tomatoes