Put sugar and water in a small saucepan over med-high heat to bring it to boil.
When the mixture bubbles and the colour has turned into an amber colour, turn the heat off.
Add hot water gradually and swirl the mixture to make it an even consistency.
Divide the caramel sauce into 4 heat proof glass cups and set aside.
Custard Pudding *3
Warm milk up to around 140°F(60°C). *2
Place egg and sugar into a mixing bowl and whisk together.
Pour the warm milk into the egg mixture gradually and stir to combine them all together.
Strain the egg mixture with a sieve and set aside.
Castella Cake Batter
Start preheating the oven to 302°F(150°C).
Place egg, sugar and honey into a mixing bowl.
Whisk all together and place the bowl over the hot water.
Continue to beat till the mixture forms soft peaks.
Add sifted flour into the batter.
Fold in the flour into the batter using a spatula.
Baking all together
Pour the custard pudding mixture over the caramel sauce in the cups.
Put the castella cake batter floating over the custard pudding mixture.
Place the cups into a deep baking tray with kitchen cloth layered at the bottom.
Pour enough hot water to reach the level of custard pudding mixture.
Bake in a preheated oven of 302°F(150°C) in the water bath for 40 minutes.
Remove the baking tray out of the oven. Take the cups out of the water bath.
Tap each cup with a spoon or fork to avoid shrinkage of Castella cake.
Serve warm or chill for later.
Notes
*1 See detail in Caramel sauce post. *2 you can warm up in any way, you can use microwave or heat up in a saucepan over cook top. *3 Read more about Japanese custard pudding.