In a large mixing bowl, whisk together the egg whites and cornstarch until a sticky paste forms.
Add the raw shrimp to the cornstarch mixture and toss well to coat.
In a large dutch oven, heat the oil until it reaches a temperature of 350 degrees. Add the shrimp, one piece at a time. Cook for 3 minutes, or until batter is lightly browned. Remove the shrimp from the pot and drain on a paper towel lined bowl. Continue to fry remaining shrimp.
In a small mixing bowl, stir to combine the mayonnaise and sweet chili sauce. Place the fried shrimp in a clean mixing bowl and pour the sauce over top. Toss to coat the shrimp with the sauce. Before serving, sprinkle with green onion tops, if using