Place short ribs in a large pot and fill with water until ribs are just covered.
Place pot over stove and bring to a boil. Boil ribs for 20 minutes.
Drain and rinse excess fat off short ribs.
Place ribs back into the pot along with soy sauce, sugar, Asian pear, garlic, mirin, sesame oil, black pepper, and 2 ½ cups water.
Cover pot and bring to a boil. Boil for 20 minutes.
Add potatoes and carrots to the pot, cover and simmer for 45 minutes to an hour.
Serve braised short rib stew over rice and top with green onions and sesame seeds.