Bring water to boil, add in ½ tsp salt, blanch prawn for 1½ minutes, drain and set aside.
Prepare chili dipping sauce: Mix 50 ml water, 2 tsp vinegar, ¼ tsp salt, 30g sugar, 1 clove of pressed garlic and 1½ tsp of chili powder. Bring the mixture to boil in a saucepan, keep stirring until all sugar has dissolved, reduce to medium-low heat and simmer for about 1 to 2 minutes, keep stirring. Mix 1 teaspoon of tapioca starch with 1 tablespoons of water, Add in to chili sauce, keep stirring until the sauce has thickened.
Cut a bulb of scallion into thin slices.
Mix 150 g rice flour, 50 g all-purpose flour, 2 tsp baking powder, 1 tsp salt, 1 tsp sugar, 1 tsp pepper and ½ tsp chicken stock powder. Add 3 Tbsp oil to flour mixture. Mix together 1 egg and 200 g water, whisk the batter until smooth with no visible lump, add in sliced scallion.
Heat oil together with a stainless steel ladle or wok spatula to 160°C.
Scoop in some batter and place a few prawns on top, as many as you prefer. Submerge batter into hot cooking oil, half-done fritter should slide into the oil. You may use a chopstick or skewer to gently push prawn fritter off the wok spatula. Fry to golden brown on both sides.
Dip in homemade garlic chili sauce and serve immediately.