Start this a day ahead and freeze overnight. For the crust, blend crumbled vanilla wafer cookies in a processor until crumbs form.
- 1/3 cup chopped pecans
- 2 tablespoons sugar
- 2/3 cup vanilla wafer cookie crumbs (from about 32 cookies)
- 1/2 teaspoon ground cinnamon
- 2 tablespoons (1/4 stick) unsalted butter, melted
- 2 tablespoons boiling water
- 1 tablespoon instant espresso powder or instant coffee powder
- 1 cup sugar
- 2 tablespoons unsweetened cocoa powder
- 1 cup whipping cream
- 1/4 cup light corn syrup
- 2 ounces unsweetened chocolate, finely chopped
- 2 tablespoons (1/4 stick) unsalted butter
- 1 1/2 teaspoons vanilla extract
- 2 pints caramel ice cream (such as dulce de leche)
- 1/2 cup chilled whipping cream
- 1 tablespoon powdered sugar
- 2 tablespoons chopped pecans
Preheat oven to 350°F. Blend pecans and sugar in processor until pecans are finely ground. Add cookie crumbs and cinnamon and process to combine. Add butter and blend until moist clumps form. Press crust onto bottom and up sides of 9-inch glass pie dish. Bake until crust is lightly toasted, about 10 minutes. Cool completely.
Stir 2 tablespoons boiling water and coffee powder in small bowl until powder is dissolved. Whisk sugar and cocoa in heavy medium saucepan. Whisk in 1 cup cream, corn syrup, and coffee mixture. Add chocolate and butter. Bring to boil over high heat, stirring constantly. Reduce heat to medium and simmer until slightly thickened, stirring occasionally, about 4 minutes. Cool 30 minutes. Stir in 1 teaspoon vanilla.
Soften 1 pint ice cream at room temperature 15 minutes. Spread evenly over bottom of crust. Drizzle 3 tablespoons sauce over ice cream. Freeze until sauce sets, about 15 minutes.
Meanwhile, soften remaining 1 pint ice cream at room temperature 15 minutes. Spread evenly atop sauce. Drizzle with 3 tablespoons sauce. Freeze pie until frozen, at least 4 hours. (Sauce and pie can be made 1 day ahead. Cover and refrigerate sauce. Keep pie frozen.)
Rewarm mocha fudge sauce over low heat, stirring often. Whip 1/2 cup chilled cream, powdered sugar, and remaining 1/2 teaspoon vanilla in medium bowl until peaks form. Transfer to pastry bag fitted with star tip. Pipe rosettes of cream around top edge of pie. Sprinkle with chopped pecans. Cut pie into wedges and serve with sauce.