Mix the mung bean starch with 1 cup of the water in a measuring cup with a pour spout until the starch has dissolved.
Bring the remaining 2 1/4 cups of water to a boil in a medium sauce pan. When it begins to boil, lower heat to medium-low and slowly stream in the mung bean starch slurry while whisking vigorously. The mixture will begin to thicken quickly. After all the slurry is added, cook for about 1 minute longer, whisking continuously so that lumps don't form. Pour and spoon the thick jelly into a 9-inch square cake pan (or similar size bowl) and set it aside to cool and firm up.
Press the garlic clove through a press or smash to a paste in a mortar and pestle. Mix the garlic paste with 2 tablespoons water and allow it to sit at room temperature while the noodles cool.
When noodles are set, which will probably be within 1 hour, turn them out onto parchment paper or a cutting board. Use a knife to cut the block of jelly into noodle shapes, about 1/4 inch wide and deep and 3 inches long. Or to your desired shape and size! Thin is better, since they don't absorb sauce easily.
Mix the sauce ingredients in a measuring cup or bowl: chili oil, Zhenjiang vinegar, Chinese light soy sauce, sesame oil, sugar and garlic water. Stir until slightly emulsified.
Pile the noodles nicely in a serving bowl and pour the sauce over them. Garnish with scallions and peanuts and serve at room temperature.