Wash, quarter, peel, core and cut the quinces into small pieces. Peel and chop the onions
Bring quinces, onions, apple juice, sugar, vinegar and mustard seeds to the boil and simmer open over a low heat for about 1 hour, stirring occasionally. Remove from heat and season with salt and pepper. Fill chutney into prepared twist-off glasses (makes 3 glasses of approx. 300 ml each) and close them. Let it cool down upside down
Fry the cured pork loin in hot oil for 3-4 minutes on each side. Season with pepper and a little salt. Arrange the pork loin and some chutney, garnish. Serve with mashed potatoes and melted marjoram butter