Cut banana leaves into about 4 inch square and brush with some oil
Prepare the dough:
Put the yeast, water and sugar in a small bowl. Stir to combine and then let it sit for 10 minutes. The mixture will turn foamy and bloom. This shows that the yeast is active
Cut the gula Melaka into smaller pieces. Put them inside a saucepan along with the water. Let it simmer until the sugar melts. Let it cool down to at least lukewarm (so it won't affect the yeast)
In another bowl, mix all-purpose flour, sticky rice flour, and activated yeast. Whisk to combine. Add this into the gula Melaka mixture. Add the oil. Stir to roughly combined and then knead until you get a dough. Cover and rest for 15 minutes. Then go back and knead into a soft and smooth dough
Shaping:
There is no need to do bulk fermentation/proofing with hee pan. Divide the dough into 6-8 equal pieces. Oil both of your palms just lightly and pull and tuck each dough to form a round smooth ball. Place each ball on top of the banana leaf you prepared earlier. Gently flatten a little bit with your palm. Repeat with the rest of the dough and banana leaves
Proofing:
Cover with a clean tea towel and put at a warm place to let them proof for at least 1 hour (no less). It may take longer than 1 hour in a colder climate. I found that if the dough is properly proofed, the hee pan will have fluffy with a slightly chewy texture. They will puff up to about 50% of its original size and feels really light. If you gently press with your finger, it will bounce back slowly
Steaming:
Fill the steamer with enough water. Place the proofed dough inside the steamer, allow some room for the dough to expand. Close the lid. Turn on the heat to medium. If you are not using a bamboo steamer, wrap the lid of your steamer with a cloth to prevent condensation drips on the surface of the buns
Turn the stove on and adjust the heat to medium. When the water comes to simmer, crack the lid open to allow some gap a bit to let steam escape. Start the timer and set it to 15 minutes and let them steam over medium heat with the lid slightly opened and DO NOT crank up the heat. When 15 minutes are up, allow 5 minutes before opening the lid
Then gently uncover the lid and transfer the buns to a cooling rack. They can be served warm or room temperature