You can follow this homemade taro/yam paste recipe. You only need 1/4 of the recipe, unless you don't mind leftovers for other use. I added a bit of ube extract (or use any purple food coloring) for a deeper purple color, this is totally optional
Steam the taro/yam:
Get about 500-600 grams of taro roots. Peel and cut into small chunks. Steam over high heat for 10 minutes or until you can easily mash with a fork. Mash while they are still warm. You can also use an immersion blender or blender to make it really smooth
Measure out 160 grams of the mashed yam to make the dough and the rest to make taro paste
Prepare the dough:
Mix the glutinous rice flour with salt, and sugar. Stir to combine. Add oil to the hot boiling water. Start with 100 ml of water and use a rubber spatula to start stirring until it forms a crumbly dough. When cool enough to handle, add mashed taro and use your hand to knead the dough into a soft, pliable and shiny dough. Add a bit more water if needed. Cover and let them rest for 10 minutes
Wrapping:
The amount of the dough and filling depends on the size of your mould. For example if I use 50-gram mould, I portion 30 grams of dough and 20 grams of filling. Roll the filling into balls for easier wrapping
Portion the dough into the size you want. Flatten them with the palm of your hand. Place the filling in the middle and bring all edges together and roll them into a smooth ball again
Dust the mold with some sticky rice flour to prevent sticking and gently knock off excess flour. I roll the dough ball into the flour thinly too. Place the dough ball into the mold. Slightly press it down as you stretch them out to fit the mold. Knock the mold once on a countertop (lined with some cloth to minimize banging sound) and the dough will flop out of the mold. Place individual ang ku kueh on a greased banana leaf or parchment paper if you don't have the leaves
Steaming:
When the water in the steamer is boiling vigorously, place the ang ku kueh inside the steamer about 1/2-inch apart. Lower the heat to medium and when you cover the lid, let it crack open about 1/2-inch and steam for 10-15 minutes, depending on how big your ang ku kue. This is very important as it helps to maintain the imprints on the cake and to make sure you ang ku kueh is not flattened. If you steam them on high heat with all the steam trapped inside ,all the imprints will mostly be blurred and the cake will expand to the side and flattened.
To test for doneness, get one ang ku kueh out and cut it open to check the inside. It should be cooked through and not "doughy" and mushy. If it is, steam a bit longer
Remove from the heat onto a plate and then brush with some cooking oil if you like. Let them cool down completely
Serve:
Let the ang ku kueh cool down completely before serving
How to store:
They can be kept at room temperature (where humidity is low) for about 3 days. If you keep them in the fridge, you just need to reheat them in the steamer for 3-5 minutes, as the skin will toughen. But once reheated, they will be soft again
The cooked ang ku kueh can also be kept frozen in the freezer for up to 3 months and they go from freezer to steamer and steam for 8-10 minutes or until heated through