In a mixing bowl, add flour, cornstarch, baking powder, garlic powder, sea salt and freshly ground black pepper. Whisk until the ingredients are well blended before transferring the flour mixture to a shallow container. In another shallow container, beat eggs and milk together.
Working in batches, dredge the chicken pieces in the flour mixture until well coating. Shake off any excess flour and dip them in the egg mixture; toss to coat. Return the chicken pieces back to the flour to dredge them a second time – this will make them crispier.
In a skillet over medium high heat, add oil and bring the temperature to 375ºF/190ºC. Working in batches, carefully add the coated chicken pieces and fry them until nicely brown, about 3 to 4 minutes, flipping them a couple times.
Transfer them to a plate or baking sheet lined with paper towels to absorb any excess oil; set aside while frying the others.
Transfer them to a large bowl and pour sweet chili sauce over; stir until well coated. Sprinkle on the sesame seeds and stir once again until evenly distributed. Before serving, sprinkle on some sliced green onions.