Hi, I live in Mexico and here you can't find the trifle sponges mentioned in some of Nigella's recipes. What could I use insted of them?
Trifle sponges are a somewhat British ingredient but are no more than dry sponge cakes. As the cakes are dry they have the capacity to soak up a fair amount of liquid in a trifle, which makes them soft and also flavours the sponges.
There are some alternatives you can use. Probably the easiest is the Italian Savoiardi or ladyfinger cookies. These are dry sponge cookies normally used in Tiramisu, but they are also good for a trifle. You could also use slices of pound cake, but as pound cake tends to be failry moist we would suggest cutting the cake into slices around 1/4-1/2 inch thick and laying the slices on a wire rack. Let the slices stand overnight to dry out a bit, or bake them in a low oven (around 120c/250F) for 30-40 minutes, carefully turning the slices over every 10 minutes, until they feel slightly dry (cool completely before using).
If neither of these are available to you then you could make a vanilla sponge cake (such as a pound cake or a madiera cake) to use. A whisked sponge would also be a good cake to make as it has little or no fat in it so dries out very quickly. If you are searching for a whisked sponge recipe then quite often Swiss roll (jelly roll)cakes are made using a whisked sponge recipe so look for vanilla versions of thie recipe.