1.Place potato in a medium saucepan, cover with cold water, bring to the boil; boil for 10 minutes or until tender. Drain;
2.Combine tomato, basil, half the glaze and half the oil in a medium bowl; toss to combine.
3.Cook lamb on a heated oiled grill plate (or grill or barbecue) for 4 minutes each side or until cooked as desired. Cover to keep warm.
4.Heat milk in a small saucepan until hot (do not boil). Add milk, remaining oil and garlic to potato; mash until smooth. Stir in olives. Season to taste.
5.Serve lamb with tomato salad and black olive mash, drizzle with remaining balsamic glaze.
Balsamic glaze is a thick reduction of balsamic vinegar; it is made from grape must (the freshly pressed grape juice from young grapes that contains the skins, seeds and stems of the fruit) and balsamic vinegar. It is available from most major supermarkets in the condiment/vinegar aisle.