Make 3 slashes on each of the drumsticks. Mix together the soy, honey, oil, tomato purée and mustard. Pour this mixture over the chicken and coat thoroughly. Leave to marinate for 30 mins at room temperature or overnight in the fridge. Heat oven to 200C/fan 180C/gas 6.
Tip the chicken into a shallow roasting tray and cook for 35 mins, turning occasionally, until the chicken is tender and glistening with the marinade.