Heat Canola Oil in large Dutch Oven on High Heat. Working in batches, brown Short ribs on all sides, a minute or so per side. Remove meat and hold to the side.
Add onions, leeks, garlic, and ginger. Cook until soft, while scraping meat bits from bottom of oven to capture flavor.
Add soy sauces, both vinegars, apple cider, brown sugar, and chili flakes to oven. Add browned short ribs. Top off with water until short ribs are just submerged. Put on cover, and simmer for 4+ hours over very low heat, or until fork tender.
Remove short ribs from pot. Boil remained liquid until reduced substantially into a thin gravy. After 10 minutes, add plums until soft, and continue reducing until sauce reaches desired thickness. Add water if you need more time. Return short ribs to pot, turning to coat. Remove pot from heat, cover, and let stand for 30 minutes.
Serve with Jasmine rice and roasted broccoli