Prepare the chocolate pudding first. Place the milk, sugar and chocolate in a medium saucepan. Cook, stirring, over medium heat until the chocolate is melted and the mixture is on the verge of boiling. Sift the cornstarch and cocoa powder together. Add water and mix thoroughly. Stir the cornstarch mixture into the chocolate mixture. Whisk in the whole eggs and the extra egg yolks. Cook until thickened (about 5 minutes). Add the vanilla extract. Pour into a bowl. Cover with plastic wrap and chill. Cut the chocolate cake into 8 cm squares. Layer half the pieces of chocolate cake in a large trifle or other large glass bowl, cutting the pieces to fit. Arrange half of the banana slices around the sides of the bowl and on top of the cake. Spread half the chocolate pudding over the cake and around the sides. Repeat the process with another layer of cake, more banana slices and the rest of the chocolate pudding. Whip the whipping cream and slather over the top of the topmost layer of chocolate pudding. Sprinkle with slivered almonds and garnish with cherry halves. Chill. Joel Ehrlich