Preheat the oven to 200C/180C Fan/Gas 6.
For the chicken, mix the sesame oil, honey and soy sauce together in a large bowl. Cover the chicken in the marinade and leave for 5 minutes.
Heat a frying pan until hot. Remove the chicken from the marinade, reserve the marinade mixture. Fry the chicken for 2-3 minutes on each side. Transfer the chicken to the oven and roast for 5 minutes, or until cooked through.
To make the stir-fry, heat the oil in a small frying pan. Add the garlic, leeks and pepper and cook until soft. Pour in the marinade mixture and bring to a simmer, continue to cook until the mixture is thick.
Spoon the stir fried vegetables into the centre of a plate, put the chicken on top and serve.