In a bowl, mix mung bean starch with ½ cup of water until fully integrated.
Heat up the remaining 3 cups of water in a saucepan until you see lots of bubbles start to appear at the bottom (Keep a close eye to avoid overheating it).
Turn the heat to low. Stir the starch mixture well, then pour into the water. Stir constantly with a spatula for 1-2 minutes.
When you see big air bubbles coming up to the surface and the mixture becoming quite thick and sticky but still runny, remove the saucepan from the heat (watch the video below for reference).
Pour the translucent mass into a heat-proof container. Leave it to cool uncovered. Then cover with a lid and store in the fridge until it turns into a block of white, solid jelly. It takes 2-3 hours.
Cut the noodles
Put one hand over the jelly, then flip the container upside down. It will slide off onto your hand easily. Put the block onto a chopping board.
Use a knife to cut the jelly into noodle strips of your preferred thickness (See note 3 for an alternative method). Transfer them to a serving plate/bowl.
Season the dish
In a small bowl, mix minced garlic, light soy sauce, black rice vinegar, sesame oil, chili oil and salt (if needed). Pour it over the jelly noodles. Top with scallions and fresh chili (if using).
You can keep the jelly refrigerated for up to 3 days. Slice and season whenever you want to serve the dish.
Be aware that the jelly will become firmer and more brittle over time. So if you plan to serve it after more than 1 day, increase the water by ½ cup when cooking it.
1. Mung bean starch can be replaced with pea starch. You can find them in Chinese/Asian stores. Other types of starch, such as cornstarch, potato starch, sweet potato starch, and tapioca starch, are not suitable for this recipe.2. If you don’t have homemade chili oil at hand, please feel free to use shop-bought spicy sauces to substitute. Laoganma spicy black bean sauce is a good alternative.3. Apart from cutting with a knife, you may also use a special jelly scraper to produce thin round noodles. See details in the post above.