01 - Season beef cubes evenly with kosher salt and black pepper, ensuring all sides are coated.
02 - Heat vegetable oil in a large Dutch oven over medium-high heat. Working in batches to avoid overcrowding, sear the beef cubes until browned on all sides, approximately 3-4 minutes per batch. 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 until fragrant and onions are softened, stirring frequently to prevent burning.
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 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 the pot with a tight-fitting lid, and braise for 1 hour. Maintain a gentle simmer throughout.
07 - Remove the lid and add quartered mushrooms. Stir gently to incorporate. Replace the cover and continue braising for another 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 - Serve hot in bowls, generously garnished with chopped fresh cilantro, sliced scallions, and additional lime wedges on the side.