To make Brit-style steak sauce:
Boil balsamic vinegar in a large, wide frying pan over high until reduced by half, 2 to 3 min. Add remaining ingredients to pan. Continue boiling, whisking often, until slightly thickened and reduced to 1 cup, 2 to 4 more min. Cool completely.
To make Chicken-wing baste:
Prick 1 kg chicken wings with a fork. Marinate with 1/2 cup Brit-Style Steak Sauce. Refrigerate at least 1 hour. Preheat barbecue to medium. Oil grill. Barbecue wings, with lid closed, brushing with 1/2 cup more sauce halfway through, until wings are cooked, about 12 min.