Preheat the oven to 190'C.
Make sure the butter and water you are using to make the pastry are cold.
Place the flour, butter and salt in a bowl and rub between your fingertips until the mixture resembles fine breadcrumbs. Make a well in the centre and slowly add the water. Bring the pastry together by hand, kneading lightly until you have a smooth ball
Wrap the pastry in cling film and chill for at least 20 minutes.
Brush a deep, loose-bottom, 24cm tart tin with oil. Set a small ball of pastry aside and roll out the rest on a lightly floured surface. Lift the pastry into the tin using the rolling pin and press into the sides. Press any cracks together and let the excess overhang.
Use the small ball of pastry to press the tart case into the flutes around the sides of the tart case and trim the edges, saving a little more pastry for later. Prick the base lightly with a fork and chill the tart case, preferably in the freezer, for at least 30 minutes.
Line the pastry with baking parchment and fill with baking beans. Transfer to the oven and bake for 20 minutes. Remove the beans and the baking parchments and then return the pastry to the oven for 5 more minutes.
Reduce the oven temperature to 140'C.
Place the fish in a pan and cover with the milk. Bring to the boil, remove from heat and then leave to stand for 5 minutes before removing from the pan. Strain the poaching liquid into a bowl and add the cream, eggs and egg yolks. Whisk together.
Peel and finely slice the onions. Pick and chop the parsley.
Add to a hot pan with a little oil and cook over a high heat until they begin to colour. Add a pinch of salt, reduce the heat and carry on cooking until the onions are soft but retain a little bite. Add the parsley and then combine this mixture with the cream and eggs. Flake the fish into the mixture and then pour into the pastry case.
Bake in the oven for 40-50 minutes and then leave to cool in the oven for an hour before slicing.
«Try using a different smoked fish such as mackerel or salmon in this recipe.»