You'll want a 12-cup (3 L) serving bowl -preferably glass- for this extravagant dessert. Raspberry Sauce: In food processor or blender, puree raspberries and icing sugar. Strain. Stir in liqueur. ( Sauce can be refrigerated for up to 3 days.) Custard: In large saucepan, heat milk and cream until hot. In bowl, beat eggs with sugar until light, about 3 minutes; whisk in flour until smooth. Pour in hot milk mixture, whisking constantly. Return to pan; cook, whisking constantly, until boiling. Stir in liqueur; simmer, whisking, for 2 minutes. Stir in vanilla. Pour into bowl; place plastic wrap directly on surface and let cool to room temperature. ( Custard can be refrigerated for up to 8 hours.) Chocolate Truffle Sauce: In top of double boiler over simmering water, melt chocolate, cream and liqueur, stirring. Let cool to room temperature. Assembly: Cut cake into 3 layers. Drizzle 1/2 cup Raspberry Sauce over bottom and sides of serving bowl. Place 1 cake layer on bottom; drizzle with 2 tbsp of the liqueur. Pour one-third of Custard over cake. Drizzle with one-third remaining Raspberry Sauce. Reserve 3 tbsp Chocolate Truffle Sauce for garnish; drizzle with one-third remaining Chocolate Truffle Sauce. Repeat with two more layers of cake, liqueur, custard and sauces. Refrigerate for at least 8 hours or up to 1 day. Whip cream; add remaining liqueur. Spread over top. Warm reserved Chocolate Truffle Sauce slightly; drizzle with fork over whipped cream.