Combine first 3 ingredients; reserve 1 cup mixture. Press remaining crumb mixture firmly in bottom of a 9-inch square pan. Freeze 10 minutes.
Spread ice cream over crumb mixture in pan. Sprinkle reserved crumb mixture over ice cream; gently press mixture into ice cream. Cover and freeze at least 8 hours.
To serve, let stand at room temperature 5 minutes; cut into 9 squares.