Heat oven to 350°F.
In large bowl, stir together crushed chocolate wafers, sugar, cinnamon and 1 tablespoon of chopped walnuts until well mixed. Stir in the melted butter until the mixture is evenly moistened. Press the crumb mixture evenly over the bottom and up sides of 9-inch glass pie plate.
Bake crust in 350°F oven until crust is set and firm to the touch, about 10 minutes. Transfer pie plate to a wire rack; let the crust cool completely.
Meanwhile, drain the pears in a sieve over a bowl, reserving 1/3 cup of the juice. Chop the pears and set aside.
In medium-size saucepan, stir together the 1/3 cup pear juice, the chocolate chips, coffee liqueur and vanilla. Stir over medium-low heat until smooth, about 3 minutes. Scrape filling into a medium-size bowl; let cool to room temperature.
In separate clean bowl, beat heavy cream until stiff peaks form. Gently fold the cream into the cooled chocolate mixture. Fold in the chopped pears. Spoon the filling into the cooled pie shell. Lightly cover and refrigerate for 3 hours or overnight.
Just before serving, garnish the pie with the remaining chopped walnuts.