Make crust: Preheat oven to 375ºF. In a food processor, pulse wafers and sugar until ground. With motor running, add butter until clumps form. Press mixture into a 9-inch tart pan. Bake 8 to 10 minutes, until firm; cool on a wire rack.
Make chocolate filling: Warm cream over medium heat until it just boils. Remove from heat, add chocolate and whisk until smooth. Let cool.
Make caramel filling: Over low heat, stir sugar and 1/ 3 cup water until sugar dissolves. Raise heat, bring to a boil and cook, swirling pan, until amber colored, 10 minutes. Remove from heat. Stir in cream, butter, vanilla and salt (mixture will bubble up and form lumps). Return to low heat; stir until smooth. Pour into a bowl; chill 30 minutes.
Pour half of chocolate filling into pie shell; sprinkle with nuts. Chill 25 minutes. Spread caramel over; chill 15 minutes. Pour rest of chocolate filling over; chill 30 minutes.