Spread the 1/2 cup nuts in a baking pan and toast in a 350°F oven for 5-10 minutes or until golden, stirring once or twice. Cool. In a medium mixing bowl combine flour and toasted nuts; cut in butter until mixture forms coarse crumbs. Add egg; stir until combine. Form into a ball. On a lightly floured surface, roll out dough to about 1/8" thickness. Line a 9-inch pie plat with pastry. Fold edge under and flute. Prick well. Bake in a 350°F oven about 20 minutes or until golden brown. Cool.
In a bowl beat together cream cheese and powdered sugar. Stir in 1 tbs of the cream. Beat remaining cream until soft peaks form; fold into cheese mixture. Spread in pie shell. Overlap mango slices in circles on top, reserving a few mango slices for garnish.
In a saucepan combine granulated sugar, cornstarch, and orange peel. Stir in peach nectar and lemon juice. Cook and stir till thick and bubbly. Cook and stir 2 minutes more. Remove from heat. Cool slightly. Spoon mixture evenly over mango slices. Chill 3-6 hours. Garnish with reserved mango slices and chopped nuts.