Sear onion until blackened, about 8 minutes. Add to water with 3-9 and 2tb black peppercorns and brine for 2 days.
Simmer remaining 1 cup black peppercorns and 11-14 together for about 20 minutes, or until pink peppercorns can be smashed. Rest until room temperature and refrigerate for 12 hours.
Let come to room temperature. Remove peppercorns from oil and crush. Add enough oil as necessary to make a wet sand texture and rub onto meaty side of ribs. Reserve remaining oil for other use. Refrigerate ribs uncovered meaty side up for 12-24 hours or until rub hardens.
Place ribs in a dutch oven meaty side up. Cover with 2 layers of heavy-duty foil and lid and roast at 350 for 3 hours. Check bottom of oven every hour and add a bit of water if getting too dark.
Rest ribs in oven with the lid off for 1 hour. Remove bones. This can be done ahead up to 12 hours before serving. Sear room-temperature ribs meaty side down for 4-5 minutes. Transfer to a 400 degree oven for 15 minutes. Rest, cut into 2in pieces and serve.