01 - Season beef cubes evenly with salt and pepper on all sides.
02 - Heat vegetable oil in a large Dutch oven over medium-high heat. Working in batches to avoid overcrowding, sear the beef until browned on all sides. Remove browned beef and set aside.
03 - In the same pot, add onion, lemongrass, garlic, ginger, and chilies. Sauté for 3–4 minutes until fragrant and onions are softened.
04 - Stir in fish sauce and brown sugar. Cook for 1 minute to dissolve sugar and meld flavors.
05 - Return the beef to the pot. Add coconut milk, beef broth, and carrots. Bring to a gentle simmer, stirring to combine.
06 - Reduce heat to low, cover, and braise for 1 hour.
07 - Add mushrooms, stir gently, and continue to braise covered for another 1–1.5 hours, until beef is very tender and easily pulls apart.
08 - Remove and discard lemongrass stalks. Stir in lime zest and juice. Taste and adjust seasoning with additional salt or fish sauce if needed.
09 - Serve hot over steamed jasmine rice or rice noodles, garnished generously with fresh cilantro, scallions, and lime wedges on the side.