01 - Season beef cubes generously with kosher salt and black pepper, ensuring even coverage 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 red chilies. Sauté for 3-4 minutes, stirring frequently, until fragrant and onions are translucent and softened.
04 - Stir in fish sauce and brown sugar, cooking for 1 minute to allow the sugar to dissolve and flavors to meld.
05 - Return the browned beef to the pot. Pour in coconut milk and beef broth, then add carrots. Bring the mixture to a gentle simmer, stirring to combine.
06 - Reduce heat to low, cover tightly, and braise for 1 hour. Maintain a gentle simmer throughout the cooking process.
07 - Add quartered mushrooms to the pot, stir gently, and continue braising covered for an additional 1 to 1.5 hours, 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 hot braised beef into serving bowls. Garnish generously with chopped fresh cilantro, sliced scallions, and additional lime wedges on the side.