In a saucepan, mix milk, egg yolk, vanilla essence, sugar, flour, and cornstarch.

Stir continuously over low heat until thickened (about 5 minutes).

Cover with cling wrap and let cool.

In a bowl, whisk eggs, salt, and sugar for 8-10 minutes until light and airy.

Gradually mix in vegetable oil, then add milk and stir well.

Sift in cake flour and baking powder, then mix until smooth.

Pour the cake batter into a greased baking mold.

Pipe or spoon the custard filling over the batter in a circular motion.

Sprinkle raisins evenly on top.

Arrange thinly sliced apples like petals on top.

Mix egg yolk and milk, then brush over the apples.

Bake at 220°C (428°F) for 40-45 minutes, until golden brown.

Sprinkle with icing sugar for a finishing touch.

Slice and enjoy warm or at room temperature!