Magic Custard Cake

"The most important thing in this recipe is that all of the ingredients are at room temperature and that the milk is not too warm, or else it might scramble the eggs. I used free-range eggs that are smaller than regular ones. If you have large eggs, use 500 ml of milk. If you don’t have a vanilla pod on hand, use 1 teaspoon of vanilla extract instead. It is also crucial that you fold the egg whites gently into the batter. The batter will be very runny, but that’s perfectly fine. The cake is done when it still has a slight jiggle in the middle. It has to be chilled in the refrigerator for at least 2 hours before serving. It’s best eaten the same or the next day. After that, it becomes very rubbery...."