For a spicier stir-fry, add even more cayenne. Or if a milder dish is in order, simply cut back the amount of cayenne.
In a large bowl, mix together the soy sauce and sherry. Add the chicken and stir to coat. Marinate for at least 15 minutes.
eat a flat-bottomed wok or large skillet over high heat until almost smoking. Add the oil to the pan and swirl to coat the pan. Immediately add the scallions and a large pinch of salt. Cook, stirring constantly, until the scallions wilt and smell fragrant, about 30 seconds. Add the garlic and ginger and stir constantly for 10 seconds. Add the chicken, any leftover marinade and the cayenne and cook, stirring constantly, until the chicken is cooked through, about 1 minute. Turn off the heat and add the sesame oil. Stir then serve.