1. Mix crumbs and butter in medium bowl.

2. Press into bottom of 8 diameter springform pan. Refrigerate crust while preparing mousse.

3. Melt 6 oz. white chocolate in top of double boiler set over simmering water, stirring until smooth.

4. Cool slightly.

5. Bring sugar and water to boil in heavy medium saucepan, stirring until sugar dissolves.

6. Continue boiling without stirring until candy thermometer registers 238 degrees (soft-ball stage).

7. Meanwhile, using electric mixer fitted with clean dry beaters, beat egg whites with cream of tartar in large bowl until soft peaks form.

8. Gradually beat hot syrup into whites.

9. Continue beating until mixture is stiff and glossy and bottom of bowl cools to barely lukewarm, about 3 minutes.

10. Fold in warm chocolate.

11. Refrigerate chocolate mixture until cool but not set, about 5 minutes.

12. Whip cream, Grand Marnier and vanilla in another large bowl until soft peaks form.

13. Gently fold cream into chocolate mixture.

14. Fold in chopped white chocolate.

15. Pour mixture into crust; smooth top with spatula.

16. Sprinkle top with chopped pistachios.

17. Freeze until firm, about 6 hours.

18. (Can be prepared 3 days ahead; cover with plastic.

19. ) Remove pan sides.

20. Cut dessert into wedges.

21. Serve with raspberry sauce.

22. For raspberry sauce: Puree raspberries in food processor or blender.

23. Strain into medium bowl to remove seeds.

24. Stir in sugar and Grand Marnier.

25. Refrigerate until well chilled, about 1 hour.

26. (Can be prepared 3 days ahead; cover).

27. (From Bon Appetit, May 1990).