Whisk the soy sauce, lime juice, sunflower oil, jalapeno pepper, garlic, ginger, coriander, brown sugar and lime zest together in a bowl until the sugar dissolves. Place the chicken into a resealable plastic bag, and pour in the marinade. Mix to coat chicken, then seal bag and refrigerate at least 2 hours.
Heat a large, nonstick frying pan over medium-high heat. Remove the chicken from the marinade and shake off excess. Place into pan, skin-side down, and cook until the skin crisps, about 4 minutes. Turn chicken over, and continue cooking on the other side until no longer pink in the centre. Remove the chicken and keep warm.
Pour the remaining marinade into a frying pan. Dissolve cornflour in water, and stir into the sauce until thickened and clear. Bring the mixture to a boil, reduce heat to medium-low, and simmer 5 minutes. Serve chicken with sauce.