Whisk together the honey mustard, chilli sauce, eggs and sea salt in a bowl. Place the chicken drumsticks in a large, resealable food bag; pour the marinade over the chicken and seal the bag. Allow to chill in fridge for at least 4 hours.
Preheat an oven to 180 C / Gas 4.
Place the panko breadcrumbs in the bottom of a wide dish; dredge the marinated chicken in the breadcrumbs to coat. Heat the vegetable oil in a large, deep pan over medium-high heat. Gently add the breaded chicken into the hot oil until golden brown, 5 to 7 minutes, turning once if needed to get even colouring.
Transfer to a baking tray and continue to cook in preheated oven for about 30 minutes, or until cooked through.