Using a fry pan on medium heat, fry the lamb roast for 3 minutes on each side, until sealed.
Place roast on baking tray and bake for 15mins.
To prepare the gravy, heat oil in a saucepan, add onion, garlic & rosemary and cook on a low heat for 2 minutes. Add Gravox and water, stirring briskly to remove lumps. Simmer for 2 minutes until thickened.
Steam the cauliflower until tender.
Add butter beans, cauliflower and margarine to a large bowl and process with a stick blender, until smooth.
Steam Brussel sprouts and beans, until tender.
Remove lamb from the oven and allow to rest before carving.
Serve lamb with gravy, cauliflower mash and steamed vegetables.