To prepare the cabbage, cut in half down the length and remove core. Slice across into long strips of cabbage. To prepare the apple, peel it then cut it in half, core it then slice it thinly.
Pour the malt vinegar into a measuring jug then top up to 230ml with cold water and add several good twists of black pepper. Set aside.
Put the cabbage into a large pan, add boiling water and blanch for a couple of minutes. Then drain immediately to stop it losing colour.
Then back into the pan and layer up the red cabbage then some apple and onion on top. Add couple of spoons of the water/vinegar mix then keep repeating. It will probably fill the pan but the cabbage will "mush" down fairly quickly. Make sure that you keep back about 110ml of the water/vinegar mix to keep adding moisture back to the cabbage as it cooks. Then back on a low heat and keep stirring it frequently to stop it catching on the bottom of the pan adding the water/vinegar when it looks like it's drying out.
Cook for about an hour stirring frequently then divide up as you need for freezing or serving. We normally have this as a Christmas accompaniment and an average red cabbage would serve four adults on Christmas day and at least that number again on Boxing Day.