01 - Season beef cubes evenly with kosher salt and black pepper, ensuring all surfaces are coated for maximum flavor penetration during braising.
02 - Heat vegetable oil in a large Dutch oven over medium-high heat. Sear beef in batches until browned on all sides, approximately 3-4 minutes per batch. Remove browned beef and set aside.
03 - In the same pot, add onion, lemongrass, garlic, ginger, and chilies if using. Sauté for 3-4 minutes until fragrant and onions are softened, scraping up browned bits from the bottom.
04 - Stir in fish sauce and brown sugar. Cook for 1 minute to allow sugar to dissolve and flavors to meld.
05 - Return beef to the pot along with any accumulated juices. Add coconut milk, beef broth, and carrots. Bring 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 gently to incorporate, and continue braising covered for another 1 to 1.5 hours until beef is fork-tender.
08 - Remove lemongrass stalks from the pot. Stir in lime zest and juice. Taste and adjust seasoning with additional salt if needed.
09 - Serve hot over steamed jasmine rice or rice noodles. Garnish generously with chopped cilantro, sliced scallions, and lime wedges on the side.