01 - Season beef cubes generously with salt and pepper, ensuring even coating 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 cubes until deeply browned on all sides, approximately 3-4 minutes per batch. Transfer browned beef to a plate and set aside.
03 - In the same pot, add onion, lemongrass, garlic, ginger, and chilies. Sauté for 3-4 minutes, stirring frequently, until fragrant and onions have softened and become translucent.
04 - Stir in fish sauce and brown sugar, scraping up any browned bits from the bottom of the pot. Cook for 1 minute to allow the sugar to dissolve and the flavors to meld.
05 - Return the seared beef and any accumulated juices to the pot. Add coconut milk, beef broth, and carrots. Bring the mixture to a gentle simmer, stirring to combine all ingredients.
06 - Reduce heat to low, cover tightly, and braise for 1 hour. Maintain a gentle simmer throughout—liquid should bubble slowly with minimal movement.
07 - Add quartered mushrooms and stir gently to incorporate. Recover and continue braising for another 1 to 1.5 hours, or until beef is fork-tender and easily pulls apart.
08 - Remove and discard the lemongrass stalks. Stir in lime zest and fresh lime juice. Taste and adjust seasoning with additional salt or fish sauce if needed.
09 - Ladle the braised beef and sauce into serving bowls. Generously top with chopped fresh cilantro, sliced scallions, and serve with lime wedges alongside steamed jasmine rice or rice noodles.