What are the trifle sponges in the Anglo Italian Trifle? I live in Australia and have never heard of them. I presume you buy a sponge cake and cut it up?
Nigella's Anglo Italian Trifle (from NIGELLA SUMMER) gets its name from the traditional fruit and sponge base of a trifle but with a tiramisu-style topping. The recipe uses trifle sponges and these are a particularly dry type of sponge that are sold in British supermarkets. As the sponges are dry they absorb liquid easily and so will soak up the limoncello and fruit juices without becoming too heavy.
Trifle sponges are easy to find in the UK but more difficult elsewhere and the best alternative is sponge finger biscuits (also known as savoiardi or ladyfingers). These are dry and light and will also soak up the liquids well. If these are not available as an alternative then you could use a plain vanilla sponge cake, such as a madeira cake or pound cake. Cut the cake into slices and sit the slices on a wire rack. Let the slices stand for a day or two, so that they dry out and stale slightly, before using them in the trifle.