In a large bowl, combine 1 cup cornstarch, ¼ cup flour, ¼ teaspoon baking powder, ½ teaspoon salt, and ½ teaspoon ground black pepper. Mix these dry ingredients well.
Crack one egg into the bowl and add 1 ¼ cups cold water. Stir everything until you have a smooth batter with no lumps.
Add 1 cup cleaned small shrimps and 1 ½ cups mung bean sprouts to your batter. Gently stir until everything is evenly mixed.
Pour 2 cups of cooking oil into a deep pan and heat over medium-high heat. Test if the oil is hot enough by dropping a small amount of batter – it should sizzle and rise to the surface immediately.
Scoop 2-3 tablespoons of the shrimp mixture and carefully drop it into the hot oil. Spread it slightly with your spoon to make it thinner – this helps make it crispier.
Fry each piece for 2-3 minutes on each side until golden brown. Don't overcrowd the pan; cook only 2-3 pieces at a time.
Remove from the oil using a strainer and place on paper towels to drain excess oil.
Serve hot and crispy with spiced vinegar on the side for dipping.
If you have leftovers, let them cool completely before storing in an airtight container. Reheat in the oven at 350°F for 3-5 minutes to make them crispy again.