1.Preheat oven to 180°C.
2.Combine breadcrumbs, herbs, garlic and pesto in a small bowl. Press breadcrumb mixture onto lamb racks. Cover and refrigerate until required.
3.Place potato in large shallow baking dish. Spray with oil and sprinkle with salt. Roast, uncovered, for 20 minutes.
4.Place lamb on top of the potato. Roast, uncovered, for 10 minutes. Reduce heat to 160deg and cook about 20 minutes or until potato is tender and lamb is cooked as desired.
5.Melt butter in large frying pan and stir leek until soft. Stir in stock and wine; bring to a boil. Reduce heat and simmer, uncovered, until liquid reduces by half.
6.Stand lamb 5 minutes before cutting racks into cutlets; serve cutlets with potato and leek.