CRUST: Combine over hot (not boiling) water, half C chocolate chips and butter, stir until chips are melted and mixture is smooth. Add chocolate wafer crumbs, stir until well blended. Press into 23 cm pie pan. Chill until firm. FUDGE SAUCE: Combine over hot (not boiling) water remaining 1.5 C chocolate chips, heavy cream, and butter. Stir until chips are melted and mixture is smooth. Remover from heat, stir in coffee flavored liqueur. Chill 10 minutes. Spread half C sauce on bottom of chocolate cookie crust. Chill 15 minutes. FILLING: In large bowl, combine ice cream and coffee flavored liqueur. Pour over Fudge Sauce layer in pie pan. Freeze several hours or until firm. Serve with remaining warm Fudge Sauce and Whipped Cream if used. Makes 1 23 cm pie