Melt the butter in a saucepan over a medium heat. Add the sugar and cook for a couple of minutes until dissolved.
Add the chopped apples and reduce the temperature to simmer gently for about five minutes until the apples are cooked and start to break down. Make sure there are still chunks of apple in the compote for texture.
Add the vanilla pod and seeds and a pinch of salt, then stew for a further minute.
Remove the pan from the heat and discard the vanilla pod. Pour into a serving dish and serve hot or cold. It will keep in the refrigerator for three days.