In food processor, place half of cookies, breaking into pieces. Process to make fine crumbs. Repeat with remaining cookies. Add half cup melted butter and process with on-off pulses, just to blend. Press crumbs evenly onto bottom and up side of 23 cm pie plate. Press crumbs evenly to rim. Bake at 160ºC for 10 minutes. Cool completely. In small saucepan, heat 6 tbls Kahlua and expresso powder over low heat until warmed and powder is dissolved. Stir in chocolate and 1 tbls butter and stir until melted and smooth. Cool completely. Transfer vanilla ice cream to electric mixer bowl and allow to soften slightly. Add 2 tbls Kahlua and beat on low speed to blend. Spread over bottom of cooled crust and freeze until firm. Spread cooled chocolate mixture over ice cream in plate. Freeze until firm. Transfer chocolate ice cream to mixer bowl; blend in remaining 2 tbls Kahlua as above. Spread chocolate ice cream over sauce in pie. Freeze until firm. To serve, pipe decorative border of whipped cream around inside edge of pie.