Lemon Custard Pies

PreparationFor Filling: Combine first 5 ingredients in heavy large saucepan and whisk to blend. Add butter. Whisk over medium heat until filling thickens and leaves path on back of spoon when finger is drawn across, about 13 minutes (do not boil). Mix in half and half and vanilla. Whisk until filling is very thick and smooth and just begins to bubble, about 6 minutes. Transfer to bowl. Cool 15 minutes, stirring occasionally. Cover; chill until very cold, about 4 hours. (Can be made 3 days ahead. Keep chilled.) For Crusts: Mix flour, powdered sugar and salt in processor. Add butter and shortening and process using on/off turns until mixture resembles coarse meal. Add 5 tablespoons water and process until moist clumps form, adding more water by teaspoonfuls if dough is dry. Gather dough into ball; divide into 2 equal pieces. Flatten into disks. Wrap in plastic and chill until firm, about 1 hour. (Can be made 1 day ahead. Keep chilled.) Preheat oven to 375°F. Roll out 1 dough disk on lightly floured surface to 12-to 13-inch round. Transfer dough to 9-inch glass pie plate. Trim overhang to 1/2 inch; reserve dough scraps. Fold edge of dough under and crimp decoratively. Repeat rolling with second dough disk; put into another 9-inch glass pie plate. Freeze until firm, about 10 minutes. Line crusts with foil; fill with dried beans or pie weights. Bake crusts until sides are set, about 20 minutes. Remove foil and beans. Continue to bake until crusts are pale golden, piercing with toothpick if crusts bubble, about 12 minutes. Cool crusts completely on racks. Maintain oven temperature. Roll out dough scraps on floured surface to 1/8-inch thickness. Transfer to baking sheet. Bake until golden, about 10 minutes. Cool. Maintain oven temperature. Crumble pastry into small pieces; wrap and reserve at room temperature. Spoon half of filling into each crust. Bake until filling is set in center, about 18 minutes. Cool pies. Chill until cold, about 2 hours. (Can be made 1 day ahead. Cover and keep chilled.) Sprinkle crumbled pastry over pies. Garnish pies with whipped cream, lemon slices and mint, if desired.