The fruit in this pie tastes lovely and fresh and the juices mingle with the rich cream and brown sugar. The crisp and nutty pastry is an irresistible contrast.
To make the pastry, sift the flour, icing sugar and salt into a bowl and stir in the chopped walnuts. Hold the frozen butter in its wrapping and coarsely grate it into the flour mixture. Mix it lightly into the flour with a fork. In another bowl, lightly whisk the egg whites with the cold water and then add to the pastry mixture a little at a time, again mixing with a fork until it begins to st