The night before serving, use an ice pick or skewers and poke holes on the skin side of the pork belly; then allow to chill uncovered in the fridge overnight to draw out moisture
Remove the pork belly from the fridge the following day to return to room temperature; preheat the oven to 200°C
Make the “BZF” stuffing:
Make caramelised onions by sautéing diced onions in a small amount of vegetable oil over medium heat, stirring constantly; once the water evaporates the onions will begin to brown; continue for 15-20 minutes until the onions are fully caramelised and sweet; set aside
Finely dice the maitake mushrooms, then rough chop the wood ear fungus (this will add texture); in a skillet with vegetable oil over medium-high heat sauté the maitake and wood ear for 5 minutes until fragrant, then deglaze with whisky; set aside
Roughly chop the roast chestnuts, then toast on a dry skillet over medium heat until dry and crunchy; incorporate into mushroom mixture
Steam the Chinese sausage until the skin can be easily removed by hand; use a fork to roughly mash up the Chinese sausage filling; set aside
In a large skillet with vegetable oil over medium-high heat add sage leaves for 1 minute until crisped up, then add the chicken liver and sauté for 5 minutes until fully changed from red to brown-grey, stirring constantly; deglaze with vin jaune or Chinese wine
Add the caramelised onions, Chinese sausage, chestnut & mushroom mixture to the chicken livers and continue to sauté for a further 5 minutes; deglaze with sherry vinegar then mix in the Pommery mustard; add salt to taste; set aside on a flat tray and allow to cool
Brush white vinegar on the pork belly skin and allow to “bleach” for 30 minutes, then use a paper towel to dab dry; pack the “BZF” stuffing on the meat side of the pork belly and roll it up, using butcher’s twine to secure the shape once rolled
Elevate the porchetta on a baking tray with a slotted rack and roast in the oven at 200°C for 1 hour
Brush some oil from the baking tray back on the porchetta skin and cut off the butcher’s twine then further roast at max oven temperature (around 250-260°C) for 15 minutes or until the skin puffs and crackles, flipping the tray mid-way; allow to rest for a minimum of 10 minutes then serve