In a large bowl, combine the Greek yogurt, egg, garlic powder, onion powder, black pepper, and salt. Add the chicken pieces and mix well to coat. Cover and marinate in the refrigerator for 15 minutes.
In a separate bowl, whisk together the whole wheat flour, cornstarch, and baking powder.
Remove the chicken from the marinade and add to the flour mixture. Toss to coat evenly. Add 1/4 cup water gradually to the flour mixture to create a thick batter that clings to the chicken pieces.
Heat the avocado oil in a large non-stick skillet over medium-high heat.
Fry the chicken pieces in batches, cooking for about 3-4 minutes per side until golden brown and cooked through. Remove and drain on a wire rack or paper towels.
In a small saucepan, combine the gochujang, low sodium soy sauce, honey, rice vinegar, sesame oil, minced garlic, grated ginger, and 1 tablespoon water. Cook over medium heat, stirring frequently, until the sauce is smooth and slightly thickened, about 3-4 minutes.
Toss the fried chicken pieces in the sauce until evenly coated.
Transfer to a serving plate and garnish with toasted sesame seeds and sliced green onions.
Serve immediately.