Combine the chicken and the marinade ingredients in a big bowl. Mix well. Marinate for at least 30 minutes at room temperature, or up to overnight in the fridge.
Combine the ingredients for the spice mix in a small bowl and stir to mix well. Note, this recipe prepares more spice mix than you might use, so you can adjust the seasoning according to your preference.
When you’re ready to cook, add the beaten egg into the bowl with the chicken. Stir to mix well. Add the cornstarch. Stir to coat the chicken, until it forms an uneven coating with a little dry cornstarch left unattached. The batter should be quite dry and not very runny.
Add the oil to a large skillet (nonstick or carbon steel), just enough to coat the bottom of the pan. Heat over medium-high heat until hot. Add the chicken one piece at a time using a pair of chopsticks or tongs. Turn to medium heat if the pan starts to smoke too much.
Cook the chicken until the bottom turns golden brown, 2 to 3 minutes. Flip to brown the other side, 2 to 3 minutes. (Alternatively, you can deep-fry the chicken with more oil at 350 F (176 C) until golden brown.) Transfer chicken to a large plate and remove the pan from the stove to let it cool a bit.
Your pan should still have a thin layer of oil remaining in it. If not, add 1 to 2 tablespoons of oil. Heat over medium heat. Spread the basil leaves. Cook the bottom side for 30 seconds. Flip to cook the other side until crispy. Transfer the basil leaves to a large plate to cool.
While the chicken is still hot, sprinkle about half of the spice mix over the chicken and gently toss it with a pair of tongs. Taste the chicken. Add more spice mix if needed. Add the cooked basil leaves and toss again.
Serve as an appetizer.
You can store the leftover chicken in a sealed container in the fridge. To reheat the chicken, preheat your oven to 350 degrees F (176 C). Heat the chicken for 10 to 15 minutes, or until heated through.