Preheat the oven to 220°C.
Place the pork belly on a lined baking tray, season the rind with coarse salt and bake for 2 hours.
Add the red onions, leeks, oil, thyme, garlic and butter to a large pot and season with 1 tsp of salt.
Place in the preheated oven for an hour.
Remove the onions from the oven and place it in a large pot over a moderate heat.
Add the onion marmalade and wine to the pot and simmer for 20 minutes.
Add the cup of vegetable stock and blend the soup with a stick blender until smooth.
Remove the belly from the oven and pull it with two forks, keeping some of the belly still quite chunky.
Serve
Top the soup with parmesan cheese and eat with fresh bread.