Place pork in a roasting pan large enough to fit pork snugly.
Stir remaining ingredients in a saucepan over medium-high heat until combined and bring to the boil.
Pour stock over pork, cover with foil and braise in oven until very tender (2-2½ hours).
Remove pork from braising liquid, cut into chunks and set aside.
Simmer half the braising liquid (save remainder and freeze in icecube trays for handy stock cubes) over medium-high heat until reduced to a glaze (10-15 minutes), then add pork and set aside.
For slow cooker
Place pork in slow cooker
Add remainder of ingredients and cook for 8 hours.
Remove pork and cut into chunks, replace into slow cooker and cook with lid off on high for a further hour.
For Okonomiaki
Combine flour, baking powder, Nippon Curry and 2 tsp sea salt in a large bowl,
make a well in the centre, add eggs and gradually add 500ml cold water, stirring until smooth and combined.
Stir in cabbage, onion, potato and pickled ginger and set aside to rest for 30 minutes.
Heat one-quarter of the vegetable oil in a 15cm-diameter non-stick frying pan over medium heat,
add one-quarter of the pancake batter, spreading evenly in pan, and cook until golden on the base and beginning to set on the surface (6-8 minutes).
Turn and cook until cooked through (6-8 minutes), then transfer to an oven tray and keep warm while you repeat with remaining oil and pancake batter.
It helps to have two frying pans on the go at once for speed.
Top hot okonomiyaki with sticky soy pork belly, spring onion and pickled ginger, and drizzle with glaze.
Serve Japanese mayonnaise, togarashi and roasted sesame seeds separately to add according to taste.