Preheat oven to 400°F. Line a large rimmed baking tray with foil and spray with cooking spray. Set aside.

Cut chicken breasts into 1-inch pieces and place them in a large shallow dish.

Sprinkle the chicken pieces with cornstarch and toss to evenly coat all sides. Set aside.

In a small bowl, whisk the eggs. Working in batches of 3-4 pieces at a time, shake off excess cornstarch, then gently toss the chicken in the beaten eggs. Place coated chicken pieces onto a large plate. Repeat until all chicken is coated.

In a very large skillet, heat vegetable oil over medium-high heat until it reaches about 350°F. Gently place half of the coated chicken pieces into the hot oil in a single layer, ensuring they do not touch and the skillet is not overcrowded. You may need to cook in 2-4 batches.

Fry the chicken for 1-2 minutes on the first side, then flip and cook for another minute. The goal is to lightly fry the chicken so the coating holds the sauce, not to cook it through.

Remove the lightly fried chicken to a paper towel-lined tray. Repeat with remaining chicken.

In a small bowl, whisk together the buffalo wing sauce, sugar, apple cider vinegar, kosher salt, and red pepper flakes to make the sauce.

Transfer the fried chicken pieces to the prepared baking tray, ensuring they are in a single layer.

Slowly and evenly pour the prepared sauce over the chicken pieces and gently toss to coat.

Bake the sauce-coated chicken for 20-25 minutes. After baking, give the chicken another toss on the tray to ensure all pieces are coated. The sauce will thicken slightly as it cools.

Transfer the cooked chicken to a large serving dish, pour any extra sauce from the tray over the top, and garnish with chopped green onions and sesame seeds.