Cut the chicken into perfectly bite-sized chunks. In a medium mixing bowl, whisk together the buttermilk and the egg until smooth. Submerge the chicken chunks into the buttermilk mixture and let rest for 10 minutes to tenderize.

In a wide shallow bowl, whisk together the all-purpose flour, cornstarch, garlic powder, salt, and black pepper. Remove chicken from the wet batter, letting excess drip off, and toss it into the dry mixture. Press the flour mixture firmly into the chicken to create a textured crust. Place on a plate.

Pour frying oil into a dark cast-iron skillet, filling it about 1 inch deep. Heat oil to exactly 350°F (175°C). Carefully drop coated chicken chunks into the hot oil. Fry for 4-5 minutes per side until crispy and golden-brown. Transfer to a wire rack.

Drain oil and wipe the skillet clean. Over medium-low heat, melt the unsalted butter until it foams. Whisk in the honey and soy sauce, letting the mixture bubble gently for 2 minutes until it becomes a glossy, rich amber honey butter glaze.

Remove the skillet from the heat. Toss the crispy fried chicken chunks into the skillet, folding gently so they are thoroughly coated in the sticky melted butter sauce. Garnish with finely chopped fresh green parsley and toasted white sesame seeds. Serve immediately.