In braising pot over MED/HIGH heat, add beef tallow until melted, sear each side of seasoned beef ribs. Remove and set aside.
Lower heat to LOW, add whole coriander, fennel and peppercorns to pan, toasting for one minute. Add oil and onion, sautee 1 min. Add garlic for 30 seconds. Add a splash of water to deglaze pan.
Place beef on top of onion and spices, nestled into one even layer. Add soy. Add enough water to raise the liquid level to about half way up the beef. Cover with parchment paper, then lid forming a tight seal. Place in oven 2.5 hours.
At 2.5 hours, remove lid and check for doneness. Meat should be jiggly and falling off the bone easily. You may need another 30 minutes here. If so, continued braising without cover and add a splash of water of it's looking too low. You don't want a dry pot!
Pressure cooker alternative
If you have a stovetop pressure cooker (Fissler, etc): after placing beef and liquids inside, seal lid and bring to 2 bars for 45 minutes.
Pickled garnish
While beef is braising, prepare your pickled items. Place in a mason jar and refrigerate while beef cooks.
Sauce
In final 30 minutes, add all sauce items to medium pan except the cornstarch slurry. Bring to low simmer. Turn off heat until just before serving. At that time, turn heat to low, bring back to simmer, adding your slurry, stirring well. This should thicken the sauce within minutes and it's ready to serve.
Sticky Rice (21 method)
In final 45 minutes of cook, soak rice in bowl of room temp water 21 minutes. Drain and rinse.
Add rice, water and salt to medium pot, covered. Over MED/HIGH bring to boil, 7 minutes. Turn heat to MED/LOW. Cook covered, another 7 minutes. Turn off heat, staying covered, allow to steam in pot another 7 minutes.
Uncover, gently fluff (it's sticky!) and pour mirin evenly over top of rice.
Serve
Serve with rice, pouring sauce over beef ribs on plate. Garnish with pickled items and chopped green onion.