Thaw 2 cups of frozen shrimp in the fridge overnight. Rinse and pat dry with kitchen towel, put them into a medium bowl. (Or you can use 1½ cup of fresh shrimp.)
Add ginger slices, salt, and white pepper powder to the shrimp, mix well. Set aside to marinate for about 5 minutes.
Add all purpose flour, baking powder, cornstarch, potato starch, water, and egg whites to a mixing bowl. Stir in one direction with a whisk until smooth.
Add ½ cup of vegetable oil to the batter. Stir in one direction with a whisk until smooth. The batter should have a custard sauce texture, it be just thick enough to coat the shrimp. (I said "mix until it looks like yogurt" in the video. But it should be thinner than yogurt. It should look like those bottled yogurt drink, e.g. Chobani.)
Pour vegetable oil into a saucepan (I added 3 cups of oil to an 1.5-quart saucepan). Heat up the oil over medium high heat to 350°F. (See tips above for how to test the oil temperature.)
Pick out the ginger slices from the shrimp. Add shrimp to batter, mix well so that each shrimp is coated with batter.
Carefully add shrimp to the oil. Deep fry the shrimp with medium heat. If your saucepan is the same size as mine, add no more than 5 shrimp at a time.
If any shrimp is stuck at the bottom of the sauce pan, gently push it with a spoon, it will bubble up and float to the surface immediately. Deep fry the shrimp for 2 to 3 minutes (based on the size) until slightly yellow.
Drain fried shrimp on a cooling rack or paper towel. Keep frying the remaining shrimp.
Once all the shrimp has been deep fried once, heat up the oil over medium high heat until it reaches 375°F. (See tips above for how to test the oil temperature.)
Add fried shrimps back to the oil to fry over medium high heat for about 30 seconds until they look golden. You can fry them for a longer time time if you want them to look golden brown.
Drain fried shrimp on a cooling rack or paper towel. Put to a serving plate.
Serve with spices seasonings or dipping sauce of your choice. (See Note below for what I used.)