Heat 40 g of fine sugar over medium-low heat until it starts melting, add in 1/2 tbsp of hot water, cook into caramel. Off the heat, add in 1.5 tbsps of hot water, mix into caramel syrup. (Reminder: Use cooking pot with thicker base to cook the caramel will prevent burning.)
Add 110 g of sugar and thick coconut milk to the caramel syrup. Beat eggs gently, add to mixture. Add plain flour to water, mix well, add to mixture. Stir until sugar has dissolved.
Sieve the mixture, then add in pandan leaves.
Bring ⅓ large pot of water to the boil, turn to medium heat, put the bowl with mixture on top of the pot (the bottom of the bowl shouldn’t touch the hot water at the bottom), cook the mixture until thickened, about 5 minutes.
Turn to low heat, cover with lid (tie with a piece of cloth to prevent water from condensation from dripping into the kaya), simmer for 45 minutes. (Reminder: Do not remove the lid while cooking.)
Discard pandan leaves, whisk kaya with hand whisk until smooth.
Transfer to a container, set aside to cool. Put on the lid when cooled, keep refrigerated. (Reminder: Prepare the kaya filling one day ahead, chilled kaya is easier to be filled into pao.)
Prepare 8 portions of kaya filling, 35 g each.