Score skin of pork belly with a knife. Baste all over with salt brine, getting in-between the cracks of the scored skin.
Rub the flesh of the pork with mustard and season generously with salt. Let the pork sit for a minimum of 30 minutes or marinade overnight for best results.
Heat oven to 180 degrees celsius, fan-forced.
Add onions and garlic to a roasting tin along with some olive oil and a sprinkle of sea salt. Place over the oven hob and sautee a few minutes until soft.
Crush cardamon pods with a knife and add to the the roasting tin along with fennel seeds, star anise, coriander seeds, and aby leaves. Stir around the pan for about 1 minutes or until fragrant.
Place pork belly on top of onion mixture and carefully pour beer and stock around the pork (but not over the skin) so that it reaches up to the side of the pork flesh, just under the fat and skin. This will keep the flesh soft and juicy whilst roasting and allow the skin to crisp up.
Roast uncovered for 2 hours.
Apple Sauce: combine all ingredients in a saucepan with a splash of water. Cook over a medium heat for 15 - 20 minutes, stirring occasionally, until the apples have broken down and are soft. Remove from the heat and allow to cool.
Remove Pork belly from oven and transfer pork to a plate or tray to rest.
Combine pan juices, with apples and whiskey and blend until smooth.
Serve pork belly with apple sauce and a side of coleslaw