Bring a large pot of salted water to a boil over medium-high heat. Add the pork leg and simmer for 15 minutes. Remove the leg, drain thoroughly, and score the rind in a crosshatch pattern.
For the marinade: Finely mince the chilli peppers (discard seeds) and garlic cloves. Mix together with soy sauce, lime juice, and honey. Stir in the oil, season with salt and pepper, then stir in the chopped parsley.
Place the scored pork leg in a large bowl or dish. Pour the marinade over it, coating all surfaces thoroughly. Refrigerate for at least 2 hours (or longer if time permits). Peel the pearl onions, celery, carrots, and parsley root, and cut them into roughly 2 cm pieces.
Heat oil in an ovenproof dish over medium-high heat. Arrange the prepared vegetables in the dish and fry for 5 minutes until starting to soften. Place the marinated pork leg on top of the vegetables. Roast at 180°C (356°F) in a preheated oven for 45-50 minutes, basting with the remaining marinade every 15 minutes.