Make the sauce by whisking the honey, lemon juice, zest and pulp together in a small bowl until blended. Stir in the plum sauce, pour into a small saucepan; set aside.
In a small bowl, combine egg with the salt and white pepper. Lightly coat the chicken with the cornstarch; dip into the egg mixture and coat in the cornstarch again. Let it stand for 5 minutes. Shake off the excess cornstarch prior to cooking.
In a wok, heat the oil until hot. Cook the chicken, a couple pieces at a time, turning occasionally, until golden brown, about 3 minutes on each side. Remove with a slotted spoon and drain on paper towels.
Bring the sauce to a boil over medium heat; add the cornstarch solution and cook, stirring, until the sauce boils and thickens.
Cut the chicken across the grain into 1/2-inch slices. Place the chicken on a serving plate. Pour the sauce on top and sprinkle with the sesame seeds.