01 - Generously season beef cubes 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, scraping up any browned bits from the bottom of the pot. Cook for 1 minute to allow the sugar to dissolve and meld with the aromatics.
05 - Return the seared beef to the pot along with any accumulated juices. 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 with a lid, and braise for 1 hour. Maintain a gentle simmer throughout the cooking process.
07 - Add quartered mushrooms to the pot, stirring to incorporate. Continue braising, covered, for another 1 to 1.5 hours until beef is fork-tender and yields easily to pressure.
08 - Remove and discard the lemongrass stalks. Stir in lime zest and juice, tasting and adjusting salt or pepper as needed. The bright citrus will balance the rich, savory sauce.
09 - Ladle the braised beef and sauce into bowls. Generously garnish with chopped cilantro, sliced scallions, and fresh lime wedges. Serve immediately while hot.