How to Make It
In the bowl of a food processor, pulse the walnuts with the flour, baking powder and salt. Add the butter and cream cheese and pulse to form coarse crumbs; pulse in the ice water to combine.
Divide the dough into 2 pieces, wrap each in plastic wrap and flatten into a disk. Freeze the dough until firm, about 15 minutes, or refrigerate for up to 2 days.
Preheat the oven to 400º. In a large bowl, toss the raisins with the apples, sugar, flour, lemon juice, cinnamon and salt.
On a piece of parchment paper, roll out one piece of dough to an 11-inch round, 1/4 inch thick. Ease one of the rounds of dough into a 9-inch pie plate and fill with the apple-raisin filling. Roll out the second disk of dough to an 11-inch round and center it over the filling. Press the edges of dough together and trim the overhang to a scant 1 inch, fold the overlay under itself and crimp with a fork. Cut a few slits in the top crust for steam to escape.
Transfer the pie to a baking sheet. Lightly brush the top crust with the egg mixture and sprinkle generously with granulated sugar. Bake the pie in the center of the oven for 25 minutes, then lower the oven temperature to 375º and bake for about 35 minutes longer, until the crust is golden and the apples are tender; cover the edge of the pie if it begins to get too dark. Let the pie cool for at least 4 hours before serving.