Use the pastry to line an eight-inch flan ring. To make the filling, cook the kipper fillets, skin and flake them. Chop and mix in the hard-boiled egg. Melt the butter in a small saucepan, stir in the flour, then remove from the heat and stir in the milk. Return to the heat, bring to the boil and simmer for a few minutes, stirring continuously. Mix in the kipper mixture, season to taste and pour into the pastry case. To make the topping, beat the egg yolks and parsley into the mashed potato. Stiffly whisk the egg whites and fold in. Pile this mixture on top of the filling and bake at 375°F, 190°C, gas mark 5 for forty-five minutes until golden-brown.