1 large tin of red salmon, 2 tablespoons butter, 1 tablespoon flour, 2 cups hot milk (if you use hot milk, you can add it al at once, instead of slowly. When I heat my milk, I also throw in 2 or 3 cloves, and a bay leaf or two), mashed potatoes, peas.
Melt the butter, stir in the flour, add the milk (if you flavour it, drain the stuff out). Stir until thick. Add the drained salmon.
Serve it with mashed potatoes and the peas.
Its probably not technically allowable for Christians that follow Lent in the correct and true forms, but its enough of a fish meal for most of us reformist Christians, and Protestants.