CRUST: In a mixing bowl combine 1 cup flour, nuts, and 1/4 t. salt. Cut in butter and shortening till mixture resembles coarse crumbs. Make a well in the center. Beat together egg yolk and water. Add to flour mixture. Using a fork, stir just till dough forms a ball.
Turn onto floured surface and knead 3 or 4 times. On a lightly floured surface roll dough to a circle 11 inches in diameter. Fit dough into a 10 inch flan pan, pressing bottom and sides gently to remove any air bubbles. Turn overlapping dough to inside and press against edges of pan. Prick sides with fork. Line bottom and sides of pan with double thickness heavy duty foil. Bake in a 400 degree oven for 10 minutes; remove foil. Cool on wire rack.
FILLING: for filling, in mixer bowl beat cream cheese and vanilla till fluffy. Add sugar, 1 tablespoon flour, and a dash salt; beat till smooth. Add the egg; beat just till combined. Do not overmix! Stir in the 2 tablespoons milk. Remove 1/2 cup of the cream cheese mixture; set aside.
combine the pumpkin, brown sugar, and pumpkin pie spice. Stir in reserved cream cheese mixture and the 1/4 cup milk. Alternately spoon the pumpkin mixture and the remaining cream cheese mixture into the partially baked crust. Using a spatula gently swirl batter to marble.
Bake in a 375 degree oven for 25 to 30 minutes or till center appears set. Cool. Garnish with pecan halves and a dollop of whipped cream and chopped nuts, if desired.