Preheat the oven to 200C/400F/Gas 6.
To make the lamb, rub the lamb with the oil and season both sides with salt and freshly ground black pepper.
Heat a frying pan until hot and sear the lamb for two minutes on both sides.
Place in the oven and roast for 10 minutes, then remove and rest for one minute.
To make the butternut squash, in a large bowl toss the squash with the olive oil, garlic and thyme then season well with salt and freshly ground black pepper.
Place on a roasting tray and cook in the oven for 15 minutes.
To make the gravy, melt the butter with the olive oil in a frying pan. Fry the onion until soft then add the brown sugar and thyme and stir.
Increase the heat and add the red wine then cook to reduce by half. Add the beef stock, season with salt and freshly ground black pepper and reduce down until thick.
Serve the squash in the middle of a warm plate, place the roast lamb on top then spoon over some of the gravy.