It is easier to shred the chicken thighs when the meat is still warm, but it can be done chilled as well. Use your fingers to release the meat from the bones and shred into pieces about ¼ inch wide.
Place the shredded chicken in a medium-size bowl. Mix the cornstarch and rice flour together in a small bowl and sift 1 tablespoon of the mixture over the chicken. Toss together with your fingers and add more sifted cornstarch/rice flour if there are uncoated pieces.
Heat a large wok with 1 inch of vegetable oil over mediumhigh heat until the oil temperature reaches 350°F. Test with a candy thermometer or 1 piece of chicken. If the oil begins to froth and sizzle rapidly, it is hot enough. If the chicken floats to the bottom of the pan and there is little movement from the oil, it is not hot enough.
Pour small batches of the dredged chicken onto a spider and shake off the excess flour. Slowly drop the pieces into the wok and shallow-fry for 2 to 4 minutes, stirring frequently, until the chicken is crisped and golden brown but not dried out. If the oil stops sizzling it needs to be hotter, so you will need to turn up the heat a notch on the stove. If the oil is smoking you can turn the flame off the stove for a second, add a small amount of oil at a time to cool down the hot oil, and turn the flame back to mediumhigh heat. When you add ingredients to hot oil it immediately lowers the temperature, and the more ingredients you add at a time, the faster the oil temperature drops, so it’s best to fry in small batches. Drain the chicken on a sheet tray or plate lined with paper towels and season with salt. Apply the same frying technique to the julienned chicken skin, without dredging in flour. The chicken skin will only need to fry for about 2 minutes to turn golden brown and crispy.
Mix the hoisin sauce with rice wine vinegar and lightly toss
the crispy chicken in the sauce. Add lemon zest and chives. Season to taste if needed.