In a large Dutch oven or heavy-bottomed pot, heat 1 tablespoon of sesame oil over medium-high heat. Brown the beef cubes in batches, about 3-4 minutes per side, then remove and set aside.
In the same pot, add the remaining sesame oil and sauté the garlic and ginger until fragrant, about 1 minute.
Return the beef to the pot and add soy sauce, brown sugar, gochugaru, and beef broth. Stir well to combine.
Bring to a boil, then reduce heat to low, cover, and simmer for 1 hour and 30 minutes, stirring occasionally.
Add the carrots, potatoes, and onion to the pot. Continue simmering covered for another 45 minutes to 1 hour, until vegetables are tender and beef is fall-apart tender.
Taste and adjust seasoning if needed. Let cool slightly before serving, or refrigerate overnight for even better flavor.
Garnish with green onions and sesame seeds before serving over steamed rice.