Preheat the oven to 180°c. Grease a 9x13-inch baking pan and dust the bottom and sides with flour, tapping out any excess flour.

For the cake - heat the butter and milk over low heat until the butter has melted. Set the mixture aside to cool slightly.

Whip the eggs, sugar and vanilla on high speed using electric beaters or a mixer fitted with the whip attachment until the eggs are doubled in volume, 5 to 7 minutes. Sift the flour, baking powder, salt and nutmeg. Fold half of the flour mixture into the whipped eggs, then add all of the butter mixture, then fold in the remaining flour mixture. Scrape the batter into the prepared pan.

Bake the cake for about 40 minutes, until a tester inserted in the centre of the cake comes out clean.

While the cake is baking, prepare the milk mixture.

Milk mixture - Stir the condensed milk, evaporated milk, whipping cream and vanilla together.

After the cake has come out of the oven and cooled for 10 minutes, poke holes in the cake using a bamboo skewer and slowly pour the milk mixture over the entire surface of the cake (the cake will absorb all the moisture and swell up). Cool the cake to room temperature.

For the topping - whip the cream until the cream holds a soft peak. Stir in the icing sugar, skim milk powder and vanilla. Top the cake with whipped cream and coco powder.

Keep the cake chilled until ready to serve. The cake must be stored and sliced directly from the pan.