Peel garlic. Peel and slice ginger 1/4″ thick. Wash scallions and cut off the root ends. Turn on the oven to preheat it to 325F.
Cut pork belly to ~5″ L x 2.5″ W x 3″ H blocks. Arrange them on the bottom of a cold skillet and place over low heat to slowly render fat.
It should take about an hour, doing it on all sides. Collect the fat to use for cooking other dishes and refrigerate or frezze. Pat dry cuts of pork belly with paper towel.
To make a cooking broth, combine the rest of ingredients and bring them to boiling, stirring. Turn off the heat, place pork belly cuts into the broth, cover with foil and place in preheated to 325F oven.
Cook for 3 hours. When pork belly is done, transfer it to containers and cover with strained broth. They should be fully submerged. Refrigerate until ready to serve. Slice cold or slightly frozen.
for sous vide pork loin chashu
Peel and thinly slice garlic and ginger. Wash scallions, cut off their root ends and chop the rest. Preheat water for sous vide to 140F/60C. Cut pork loin into three portions 1lb/500g each, tie them tight, and place inside the vacuum packing bags.
Combine sake, soy souce, mirin, sugar, and water and stir until sugar is dissolved. Divide the broth between three bags with pork equally. Divide prepared garlic, ginger, and scallions ibto three equal portions and add them to the bags.
Vacuum pack each portion of pork.
Cook for 3 hours, 140F/60C. When ready, prepare a big bowl with ice bath (ice and water 1:1). Keep the pork loin vaccum packed.
Use ice bath to quickly cool down cooked pork to room temperature and then refrigerate for 12-24 hours — it’ll continue being marinated. Slice it thinly when cold and use ramek broth to reheat it in the bowl.