In a mixing bowl, whisk together egg white, all-purpose flour, cornstarch, baking powder, ice-cold water, and one pinch of salt until just combined to make the batter.
Add the chicken pieces to the batter and toss to coat evenly.
Heat about 2 inches of oil in a wok or large deep skillet over medium-high heat until hot.
Carefully deep-fry the battered chicken in batches until golden brown and cooked through, then transfer to a paper-towel-lined plate to drain.
Wipe out the wok or skillet and heat 1 tablespoon oil over medium heat, then sauté the minced garlic until fragrant, about 30 seconds.
Add the fried chicken to the pan, pour in the Thai sweet chili sauce, lime juice, and the remaining pinch of salt, and toss to coat the chicken evenly in the sauce.
Transfer to a serving dish and garnish with white sesame seeds and chopped cilantro leaves, then serve immediately.