Https://youtu.be/O0IpMZfS_3M
To make caramel: In a heavy-bottom pot, heat sugar and 1 tbsp water over medium heat until it caramelizes or turns brown.
Turn off the heat and carefully add 1 tbsp hot water into the caramel. It will sizzle quite aggressively so watch out for any hot splatter.
Pour and divide caramel evenly into 4 heat-proof cups. Place the cups in a deep baking dish. We will bake this with a bain-marie (water bath) method. Set aside.
To make pudding: In a medium bowl, whisk eggs, sugar, and rum until combined. Then gradually add in heated milk (60C or 140F) while whisking the egg mixture. To avoid having chunks of cooked eggs, remember to keep whisking while pouring the milk. Strain the mixture into a jug. Set aside.
To make castella: Using a hand mixer, beat egg, sugar, and honey until light and thickened.
Sieve cake flour into batter. Using a silicone spatula, fold mixture just until combined. Do not overmix as it will deflate the batter and result in a dense cake.
Assembly: Pour and divide pudding mixture evenly into the 4 cups. Top each cup with cake batter until almost full.
Transfer into preheated oven at 320F or 160C. Pour as much boiling water as possible into the baking pan. Bake for 35 minutes or as long as possible until the cake top really browns. Longer baking will ensure the pudding inside is cooked through.
Out of the oven, I let them sit in the hot water bath for 10 more minutes. This allows the pudding to further set. Then remove from water and chill them overnight. Enjoy the pudding on the next day.
