Pat shrimp dry with a paper towel. In a mixing bowl, toss shrimp with fish sauce.
Put cornstarch in a separate bowl or freezer bag. Add shrimp and toss to coat.
In a small bowl, stir together salt, black pepper, Chinese five spice, and sugar. Set aside.
In a pot with a heavy base, heat ½ cup of oil over high heat. You want it to be approximately 350 to 400 F degrees. Shake excess cornstarch off the shrimp and gently lower into the oil. Fry for 1 minute, flip fry for 30 seconds. Use a slotted spoon to transfer to a plate lined with a paper towel.
Drain the oil and wipe out the pan. Heat 1 tablespoon of oil on medium. Cook garlic, ginger, and chili, stirring, for 20 seconds. Add shrimp, salt mix, and half of the onion and cilantro. Mix to coat thoroughly. Transfer to a serving plate. Garnish with remaining onion and cilantro.
