Put the chops in an ovenproof dish. Toast the onion in a pan in butter until light brown. Add the brown sugar, lemon juice and vinegar essence and bring to the boil. Pour the stock over the meat and cook on the stove for 5 minutes.
Whisk all the ingredients for the sauce and add to the chops. Cover and cook in the preheated oven to 200 degrees for approx. 40 minutes. Remove the lid during the last 20 minutes.