01 - Season beef cubes generously with kosher salt and black 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. Remove browned beef and set aside on a plate.
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 softened and translucent.
04 - Stir in fish sauce and brown sugar. Cook for 1 minute, allowing the sugar to dissolve and flavors to meld.
05 - Return the seared beef to the pot. Pour in coconut milk and beef broth. Add carrot pieces. 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.
07 - Add quartered mushrooms to the pot, stir well to incorporate, and continue braising covered for another 1 to 1.5 hours. The beef is done when it yields easily to a fork.
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 - Serve hot over steamed jasmine rice or rice noodles. Garnish generously with chopped fresh cilantro, sliced scallions, and extra lime wedges on the side.