Make the crust: Combine pecans and sugar in food processor and process until finely ground. Add flour and process to combine. Add butter and pulse until pea-size crumbles form. Add egg yolk and ¼ cup ice-cold water and pulse just until combined. Transfer to counter and knead into a disk. Wrap in plastic wrap and refrigerate for 1 hour. Heat oven to 375°. On a floured work surface, roll dough until⅛" thick. Line a 9" pie plate with dough, and prick with the tines of a fork over the bottom; bake until golden brown, about 20 minutes, and then let cool completely.
Make the candied pecans: Whisk egg white in a medium bowl until frothy and loose; add pecans and sugar and toss until evenly coated. Transfer to a parchment paper- lined baking sheet in an even layer, and bake until lightly toasted and dry, about 10 minutes. Let cool completely.
Make the ice cream: Prepare Vanilla Ice Cream according to instructions. Once churned, stir candied pecans into ice cream, and then transfer ice cream to pie crust, smoothing the top with a rubber spatula. Decorate with more whole pecans, and freeze until set, at least 4 hours.