Cut chicken thighs into cubes and add the soy sauce, pepper, garlic, cornstarch, oil, and lemon zest and set aside to marinate for 10-30 min. If the mixture isn’t wet enough, add 1-2 tbsp of water.
Heat up your oil in a large non-stick skillet on high heat. You will need about 1 1/2 to 2 cups of any frying oil and make sure it gets to about 325 degrees F before you add your chicken. To test this, drop a small piece of chicken in and if it starts sizzling then its ready. In a separate plate, add 1/2 cup of cornstarch. Coat chicken pieces fully in the cornstarch mixture. This extra step will allow for an extra crispy coating!
Once you have hot oil, fry the chicken in small batches so they have enough room to cook and get extra crispy! They should only take 3-4 minutes per side or be 165 degrees F for the internal temperature. Place chicken on a plate lined with a paper towel when finished to drain the excess oil.
To make the sauce, combine the soy sauce, corn starch slurry (just mix the water and corn starch in a separate bowl), garlic, pepper, lemon juice, zest, butter and sugar in a pan until combined. Cook on medium heat until bubbly and when the sauce has thickened, put the heat on low.
Then add in your crispy chicken and toss them until fully coated in the tangy lemon sauce! Top with sesame seeds and green onions and enjoy!