All I use for flavouring is a dry rub of five spice and salt on the flesh side, I then poke the skin with this gorgeous looking implement
!click! (Well, actually not this one as it’s new and fairly blunt – read the topic for explanation!!)
If your pork belly is of good quality then the skin should be nice and dry anyway, there will be no need to treat it with boiling water/vinegar/lemon juice etc. Besides I’m not sure how effective any of that stuff really is. Rub a mixture of coarse and fine salt onto the skin and roast as normal on a medium heat on a trivet. My idea is just to cook the meat till it’s done ignoring the crackling. I roast mine for only about an hour and fifteen in a 180C oven by which time the meat is still succulent but the crackling is nowhere near done.
Now comes the grilling/broiling part; under a moderate heat, blister the skin evenly all over until it’s just about to char. Too much and you’ll get that acrid burnt skin taste, too little and it’ll still be chewy. In a perfect world your belly will be flat (pork belly that is) and your grill will grill evenly. But the real world isn’t flat and even (literally) so you will be moving your belly around placing shunts underneath to make sure the skin blisters evenly. When you’re done the crackling will have big blisters all over and maybe a little charring – pretty unappetising. But let it cool a little (hot crackling is never crispy) then gently scrape way the top layer with a sharp knife. As you scrape an even layer of thin crispy golden crackling will reveal itself to you.
That’s it, that’s my method! My mother mentioned once that there’s an extra step the pros do with bicarbonate of soda to make the crackling even lighter, but she was hazy with the details so I’ve never experimented.
I’ve never used maltose on pork belly skin, I think that is more for ducks and geese to give that lacquered finish. Maybe it’s used for suckling pig but that is a different beast and method altogether.