Cut the chicken breasts into 1-inch chunks and pat dry with paper towels to ensure coating sticks properly.
In a large bowl, combine cornstarch, flour, salt, and black pepper. In another bowl, beat the eggs for dipping.
Dip chicken pieces into beaten eggs, then coat with the cornstarch mixture, pressing lightly to adhere.
Heat about 1 inch of canola oil in a frying pan or wok over medium-high heat until hot and sizzling.
Fry chicken pieces in batches until golden brown and crispy, about 4-5 minutes per side. Drain on paper towels.
In a separate pan, heat 2 tablespoons of oil over medium heat. Sauté minced garlic until fragrant, then add ketchup, honey, soy sauce, rice vinegar, brown sugar, and chili paste if using. Stir to combine.
Mix water and 1 tablespoon cornstarch until smooth, then pour into sauce, stirring constantly until thickened, about 2-3 minutes. Remove from heat and stir in sesame oil.
Add crispy chicken to the sauce and toss gently to coat each piece thoroughly.
Transfer to a serving platter and garnish with sesame seeds and chopped green onions. Serve immediately for best texture.