Preheat your oven to 160°C (320°F) and line the bottom of an 8-inch cake tin. In a large bowl, whisk together the heated water and 1/3 cup granulated sugar (for yolk mixture). Add the egg yolks and vanilla essence, whisking until the mixture doubles in size and becomes pale and fluffy. Mix in the neutral oil. Sift in the all-purpose flour, cornstarch, baking powder, and a pinch of salt, then gently fold into the wet mixture until just combined.

In another large bowl, beat the egg whites until foamy. Gradually add the remaining 1/3 cup granulated sugar (for whites) and continue beating until stiff peaks form. Carefully fold the beaten egg whites into the egg yolk batter from Step 1 in 2-3 additions, making sure not to deflate the mixture.

Pour the combined batter from Step 2 evenly into the prepared cake tin. Bake for 40-50 minutes, or until the cake is level and springs back when pressed in the center. Invert the cake on a wire rack to cool completely. Once cooled, refrigerate the cake to chill. Unmold the cake, gently rub the outer caramelized crust off, and set aside until assembly. For an extra light sponge, I always let the cake chill in the fridge before layering.

In a large bowl or stand mixer, combine the whipping cream, granulated sugar, and vanilla extract. Whisk on high speed until stiff peaks form. Transfer most of the whipped cream into a piping bag fitted with a large round tip for easy spreading. Reserve some cream in the fridge for final decoration.

Peel the mangoes. Cut one mango into large cubes for decorating the top of the cake. Thinly slice the remaining mangoes for layering between the cake. I find that using ripe, sweet mangoes makes a huge difference in the final flavor.

Slice the chilled sponge cake (from Step 3) horizontally into three equal layers. Place the first cake layer on a turntable and spread a thin layer of whipped cream (from Step 4) over it. Layer thinly sliced mango (from Step 5) over the cream, add more cream, and top with the next cake layer. Repeat the process, then finish with the final sponge layer. Use a palette knife to cover the cake with a thin layer of cream, spinning the turntable to get a smooth finish. Place the remaining cream in a piping bag fitted with a star tip and pipe a decorative border around the cake's edge. Decorate the top with the cubes of mango (from Step 5). Chill in the fridge for 1-2 hours before serving to help the cake set and develop flavor.