Blanch the banana leaves in hot boiling water for about 5 minutes to soften it. Pat dry and set aside.

Cut the banana leaves into 7-inch width and about 7-8 inch length. Line the leaf horizontally and then vertically like a "+" (overlapping at the bottom of the dish) and then diagonally like an "X" to make sure I cover all the side and bottom of the dish. Repeat this pattern for 2 more times. For slow cooker, skip down to slow cooker to read the instruction

Place both sugar, ginger, and water in a saucepan and bring to a gentle simmer or until sugar is melted. Remove from the heat and let it cool down completely. Remove the ginger.

Gradually pour the sugar mixture into the flour and stir until smooth. Then stir in the vanilla extract and orange zest. If there are lumps, strain it with a sieve and then pour into the pan lined with banana leaves.

Pour 1 cup of water into the inner pot and set the trivet, placing the nian gao on top. Cover with aluminum foil and close the lid. Pressure release valve to seal and press pressure cooker, high pressure. I recommend using aluminum or stainless steel pan as they conduct heat better. Set the timer to 60 minutes and then wait 5 minutes to release pressure.

The cake will still seem very soft. If you use a chopstick to poke the middle of the cake, nothing should stick to the chopstick. If there is, the cake is not cooked through yet

Let it cool down completely and then wrap with aluminum foil. Let it sit at room temperature for at least 24 hours before unmoulding or attempting to cut. They will get slightly firmer. They can be kept at room temperature for up to 1 week if it's not humid. They can be refrigerated for up to 6 months.