Cut chicken into bite-sized pieces. In a bowl, whisk 1 egg with a pinch of salt and pepper, then toss in the chicken. Add cornstarch and stir until coated.

In a separate bowl, mix soy sauce, rice vinegar, brown sugar, garlic, ginger, broth or water, and crushed red pepper.

In a small cup, mix cornstarch with cold water to make your slurry and keep it nearby.

Heat about 1 inch of oil in a deep skillet or heavy pan until hot enough that a tiny bit of batter bubbles immediately.

Fry chicken in batches, 4 to 6 minutes per batch, turning until golden and crisp. Drain on a rack or paper towel.

Carefully pour off most oil, leaving about a tablespoon in the pan. Add the sauce mixture and let it bubble for about a minute.

Stir in the cornstarch slurry and keep stirring until thickened, usually another 30 to 60 seconds.

Add the crispy chicken back into the pan and toss quickly until coated. Turn off the heat and top with sliced green onions and sesame seeds.