Place the cream cheese, butter, flour, sugar and salt in the bowl of a food processor. Process just until a dough begins to form. Turn out onto a floured surface and gather into a ball. Place on a piece of plastic wrap, flatten slightly, wrap and refrigerate for at least 2 hours.or unti chilled.
TO MAKE THE FILLING:.
Combine the prunes and orange juice in a small non aluminum saucepan. Cover and cook over low heat until the prunes absorb all of the moisture, about 15 minutes.
Place in a food processor and process until the consistency is fairly smooth.
Transfer to a bowl and stir in orange zest and walnuts.Set aside until ready to use.
Preheat oven to 400*.Cut a piece of foil to fit the bottom of a 9" square pan. Place the foil on a work surface -- Lightly butter the pan.
Remove the chilled pastry from the refrigerator and divide in half -- Place one half in the center of the foil and using a lightly floured rolling pin, roll out the dough the fit the foil -- Trim the edges flush with the foil, as needed and use the trimmings to patch the rounded corners and make them square, trimming with a small knife as needed.
Invert the foil into the prepared pan.carefully peel off the foil.Reserve the foil for the remaining pastry.
Spread the pastry lined pan with a thin, even layer of prune filling.
Roll out the remaining half of the pastry as previously described.Invert the pastry over the filling, peel off the foil.
Lightly brush the top of the pastry with the beaten egg.
Bake for 5 minutes. Reduce the heat to 350*.and bake for 25 minutes or unti the top is golden and the edges have pulled away from the sides of the pan.
Cool on a wire rack.Dust the top with powdered sugar sifted through a small strainer.