Sprinkle gelatin over cold water in small saucepan; let stand 1 minute. Stir on low heat until gelatin completely dissolves, about 5 minutes. Stir in sugar and coffee; heat until dissolved. Remove from heat; stir in whiskey and vanilla.

Place ice cream in electric blender or food processor; cover. Process until smooth. While processing, gradually add gelatin mixture through feed cap; process until blended. Pour into large bowl; let stand 2 to 3 minutes or until mixture mounds slightly when dropped from spoon. Gently stir in 1-1/2 cups whipped topping.

Spoon into prepared crust. Refrigerate until firm, at least 2 hours. Top with remaining whipped topping just before serving.

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