Pre- heat the oven to 190 °C/375°F/gas mark 5
Bring a large pan of water to the boil, add the potatoes and part boil for 5 minutes then drain. Place 4 tbsp of the oil in a large roasting tin and heat in the oven for 5 minutes until almost smoking. Quickly add the potatoes to the tin and shake about to coat with the hot oil. Add the carrots, aubergines and garlic. Roast for 15 minutes.
Meanwhile, heat the remaining oil in another roasting tin on top of the hob and sear the racks of lamb all over for 5-8 minutes. Turn the racks bone side down. Transfer the tin to the oven and roast the lamb for 10 minutes.
In a large bowl, mix together the breadcrumbs, herbs and chilli and season with salt and freshly ground black pepper. Spread the mustard over the thin layer of fat on the tops of the racks of lamb and press the breadcrumb mixture on the mustard. Return to the oven and roast for further 5 minutes until the lamb is cooked to your taste. Allow to rest while making the gravy.
Pour off and discard as much fat as possible from the roasting tin, then place it on the hob. Add the vinegar to the pan and deglaze, scraping all the bits of meat and sediment off the bottom. Stir in the red wine and stock and boil for 5 minutes until syrupy. Away from the heat, whisk in the butter. Strain through a sieve. Season to taste with salt and freshly ground black pepper. Serve the lamb with the vegetables and gravy.