Preparation

• For lemon curd:
  Whisk eggs and egg yolks in medium bowl. Melt butter in medium metal bowl set over large saucepan of simmering water. Whisk in sugar, lemon juice, lemon peel, and salt; gradually whisk in egg mixture. Whisk until thick and thermometer inserted into curd registers 178°F to 180°F, about 8 minutes. Transfer to small bowl. Press plastic wrap on top of curd; chill 4 hours.
  Can be made 2 days ahead. Keep chilled.
  
  for crust:
  Preheat oven to 400°F. Mix pecans or walnuts, sugar, and butter in medium bowl until moistened. Press mixture onto bottom and up sides of 9-inch-diameter glass pie dish (mixture will be crumbly). Bake until crust is lightly toasted, about 12 minutes (crust will slip down sides of dish). Use back of spoon to press crust back into place. Cool crust on rack. Freeze crust 30 minutes.
  
  Dollop 1 1/2 cups ice cream over crust; spread into even layer. Spread lemon curd over ice cream; freeze until firm, about 2 hours. Dollop 1 1/2 cups softened ice cream over lemon curd; spread into even layer. Cover and freeze until firm, about 2 hours.
  
  For meringue: Using electric mixer, beat egg whites in medium bowl until frothy. Beat in cream of tartar. With mixer running, gradually add sugar. Beat until stiff peaks form. Spoon meringue over pie, spreading to seal at edges and swirling decoratively.
  Can be made 1 day ahead. Freeze pie. Brown meringue until golden in a preheated 500°F oven watching to prevent burning, about 2 to 3 minutes. Cut pie into wedges; serve immediately.