CRUST:

2/3 c. chocolate wafer crumbs
1/3 c. graham cracker crumbs
1/4 c. unsalted butter, melted

DARK CHOCOLATE MOUSSE:

4 oz. semisweet chocolate, finely chopped
2 oz. unsweetened chocolate, finely chopped
6 egg yolks
3/4 c. sugar
1/2 c. Frangelico liqueur
1 1/4 c. chilled whipping cream

WHITE CHOCOLATE MOUSSE:

3/4 c. whipping cream
10 oz. white chocolate, chopped
3 tbsp. Frangelico liqueur
1 1/3 c. chilled whipping cream
2 oz. semi sweet chocolate, coarsely chopped
1 tbsp. unsalted butter

Preheat oven to 350 degrees. Mix all crumbs in bottom of 9 1/2 inch springform pan. Pour butter over and mix with fork until well blended. Press mixture firmly onto bottom of pan. Bake 8 minutes and cool on rack.

Stir semisweet and unsweetened chocolate in double boiler over barely simmering water until smooth and melted. Cool to lukewarm. Using electric mixer, beat yolks to blend in large bowl. Gradually add sugar and beat until pale yellow and slowly dissolving ribbon forms when beaters are lifted.

Blend in 1/2 cup Frangelico, then melted chocolate. Whip cream in another bowl until soft peaks form. fold 1/3 of cream into chocolate mixture. Gently fold in remaining cream. Pour mixture into crust and smooth top. Freeze until set, about 30 minutes. Bring 3/4 cup cream to a boil in heavy small saucepan, reduce heat and simmer 2 minutes. Finely chop white chocolate in processor. Pour hot cream through feed tube and blend until mixture is smooth, about 1 minute. Transfer to medium bowl. Cool completely.

Stir 3 tablespoons Frangelico into white chocolate mixture. Using electric mixer, whip 1 1/3 cups cream in medium bowl until peaks form. Fold 1/3 of cream into white chocolate mixture. Gently fold in remaining cream. Pour over dark chocolate mousse.

Smooth top and freeze until top of mousse sets. Cover mousse and freeze at least 24 hours. Run knife around edge of pan to loosen. Release pan sides from mousse, smooth sides of mousse with icing spatula. Return to freezer.

Stir 2 oz. semi sweet chocolate and butter in heavy small saucepan over low heat until melted and smooth. Cool to lukewarm. Spoon into parchment cone or pastry bag fitted with small plain tip. Pipe chocolate in decorative pattern around edge of mousse. Freeze until chocolate sets, about 10 minutes.

Can be prepared 2 days ahead. Cover with plastic wrap. Cut frozen mousse into wedges to serve. Serves 10.