Chocolate Raspberry Trifle

For Chocolate Custard: Combine cornstarch, sugar and salt in medium, heavy-duty saucepan. Gradually add milk. Whisk in egg yolks until smooth. Cook, stirring constantly, over medium heat until mixture comes to a boil. Boil, stirring constantly, for 1 minute. Remove from heat. Add 1 1/2 cups chocolate morsels; stir until melted. Press plastic wrap on surface; refrigerate. For Trifle: Beat cream and sugar until stiff peaks form. Cut cake into 1/2-inch thick slices. Cut one slice into thin strips; reserve for top. In 2-quart straight-sided bowl (trifle dish), layer half cake slices, half crème de cacao, half jam, half chocolate custard and half whipped cream. Repeat cake, crème de cacao, jam and chocolate custard layers. Top with reserved cake strips, remaining whipped cream, and remaining morsels. Cover; refrigerate for 1 hour. Garnish with raspberries; sprinkle with cocoa just before serving.