Firstly pre-heat the oven to 180°C/350°F/Gas Mark 4
Peel the potatoes and chop into cubes, then place into a saucepan, cover with water and bring to the boil. Turn down the heat and simmer until cooked. Drain off and mash with the butter and milk, season, cover and leave. Prepare the cabbage by chopping the leaved into strips.
While waiting for the potatoes to cook, get on with the duck. Place a frying pan on a low heat, season the duck breast heavily and place skin side down in the pan, continue cooking on the low heat until the fat starts coming out, draining off as you go along. Cook like this for about 10 minutes, then turn up the heat, crisp up the skin and flip over. Then pop onto a tray and finish in the oven for 5 minutes until cooked through, then take out and rest for 5 minutes
Place a pan on the heat for the green, add a little splash of water. When hot, add the cabbage, season and cook for about 5 minutes. Drain off and cover.
Then back to the sauce, drain the remaining fat out of the frying pan, and pour the sweet wine into the pan, mixing in the residue. Add the stock, soy sauce and seasoning and reduce by half, then thicken with the cornflour. Finally take off the heat and stir in the grapefruit.
Then slice the duck and serve with the mash, greens and sauce.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.