In a large pot, heat the vegetable oil over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes.

Stir in the minced garlic, ginger, turmeric, and red chilies. Cook for another 2-3 minutes until fragrant.

Add the beef cubes to the pot and brown on all sides, about 5-7 minutes.

Pour in the coconut milk and beef broth. Stir in the lemongrass, ground coriander, ground cumin, ground cinnamon, kaffir lime leaves, brown sugar, and salt.

Bring the mixture to a boil, then reduce the heat to low. Cover and simmer for 2-3 hours, stirring occasionally, until the beef is tender and the sauce has thickened.

If the sauce is too thin, uncover and simmer for an additional 30 minutes to reduce it further.

Taste and adjust seasoning if necessary before serving.