Preheat oven to 175 ºC (350 ºF) and like a baking tray with greaseproof/baking paper. Use a shallow baking tray (I've used a 10 x 14" tray 1 inch deep).
Bake at 175 ºC (350 ºF) for 25 – 30 min or until golden and a skewer/toothpick comes out clean.
Note 1: Cornflour usually isn’t a curd component, but we’ll be adding it in this case because we want our curd extra-thick so that it doesn’t cause the buttercream to become runny.
Note 2: The amount of milk in buttercream depends on the temperature of your kitchen and therefore how soft your butter is.
Note 3: The first 1/3 of meringue mixture doesn't need to be added carefully. It's a "sacrificial" amount that serves to loosen up the sponge mix.
Note 4: Refrigeration ensures that the cakes are cold enough for the chocolate drizzle to set quickly, rather than dripping all the way to the bottom of the cake.