Step 1
To make the sauce, combine the sugar, cream and butter in a saucepan over medium-low heat. Stir for 3-4 minutes or until melted and smooth. Stir in the vanilla. Reserve 2/3 cup and transfer the remaining sauce to a bowl. Refrigerate until chilled and thickened.
Step 2
Remove the icing from the cakes and discard or save for another use. Cut each cake in half horizontally to make 4 rounds in total. Cut rounds in half crossways to make 8 semi-circles. Use a small serrated knife to cut 12 Anzac biscuits in half, using a sawing motion so they don’t break.
Step 3
Place 2 of the semi-circles in the base of a 3L (12 cup) trifle bowl, pressing to fit against side. Cut a triangle from one of the remaining semi-circles, and use to fill the gap to create an even layer of cake. Scatter with half the date slices and drizzle with half the reserved sauce.
Step 4
Use electric beaters to beat the custard and mascarpone in a large bowl until firm peaks form. Dollop 1/4 of the mixture over the cake, and gently spread to the edges. Arrange Anzac biscuit halves around the edge of the bowl, standing upright (you’ll need 10 or 11 pieces). Use your fingers to break up 2 whole biscuits and sprinkle over the custard mixture. Spoon 1/3 of the remaining custard mixture inside the biscuit ring.
Step 5
Repeat the layers of cake, dates and sauce. Top with half the remaining custard mixture, then the remaining Anzac halves. Crush 2 more biscuits over the custard mixture. Chop half the remaining cake and add in the centre (you will have some cake leftover). Top with remaining custard mixture. Transfer to the fridge for at least 2 hours or up to 6 hours to chill. Decorate with whole and crushed Anzac biscuits and extra date slices. Drizzle with chilled sauce.
