In a small bowl, mix together all the dry rub ingredients: 2 tsp salt, 1 tsp freshly ground black pepper, 2 tsp shichimi togarashi, and ¼ tsp white pepper.
Remove the membrane from the underside of the ribs, pulling it down the entire length with a paper towel (because it's very slippery!). You can ask the butcher to remove it for you. The ribs on the right are without membrane.
Season the ribs with the dry rub mixture on both sides of the ribs. Here I use UchiCook's Maraca Sifter. This is so convenient to sprinkle seasonings evenly!
Use dry rub to cover all sides, and then rub in thoroughly on both sides. Set aside for 30 minutes.
To Prepare the Sauce
In a small saucepan, combine ¼ cup sake, ¼ cup mirin, ½ cup soy sauce, 1 Tbsp rice vinegar, 4 Tbsp brown sugar, and 3 Tbsp honey.
Turn off the heat. The sauce may be still liquid-like, but once it cools down, the sauce will get thicken further. The sauce will be roughly ⅔ cup after cool down.
To Pressure Cook Ribs
Place the metal steam rack into a 6-QT Instant Pot. Add 1 cup water and ¼ cup apple cider vinegar.
Put the ribs upright on top of the rack, wrapping in a circle.
Select Manual setting; adjust the pressure to high, and set time for 25-30 minutes (if you want the meat to fall off the bone, do 30 minutes). If you use spare ribs, set time for 30-35 minutes.
When finished cooking, natural release for 5 minutes, then quick release the air (be careful and cover your fingers with a kitchen towel).
To Broil the Ribs
Preheat the broiler* with a rack placed about 6" (15 cm) away from the top heating element (in the center of the oven) for 5 minutes. When broiling, you don't control the temperature in the oven; instead, you control the distance between the broiler and the surface of the food. It's similar to using hotter and cooler zones on your grill. *Broiler setting: Low (450ºF/232ºC), Medium (500ºF/260ºC), and High (550ºF/288ºC). I usually use medium (6" away) or high (8" away).
Line a baking sheet with aluminum foil and place a wire rack. Transfer the ribs from the Instant Pot to the wire rack.
Brush with the sauce on both sides of the ribs.
Place into oven and broil until the sauce is caramelized, bubbly, and brown, about 3-4 minutes.
Remove from the oven and brush more sauce on the ribs.
Sprinkle sesame seeds and chopped green onion. Serve immediately with the remaining sauce.