Preheat an oven to 350 F.
Chop and sear the beef. Cut your beef chuck into 2 inch cubes and season liberally with salt and pepper. Heat the oil in a dutch oven over medium-high heat and sear the beef until browned on all sides. Remove from the pot using a slotted spoon and transfer to a plate. Depending on the size of your dutch oven, you may need to do this in batches.
Saute the aromatics. Reduce the heat to medium and add the serranos, ginger, garlic, smashed lemongrass, turmeric, lime leaves, and curry paste. Cook for 2-3 minutes, stirring often until very fragrant.
Build the sauce. Add the water and coconut milk to the pot and bring to a gentle simmer, stirring so that the curry paste is well-incorporated. Add the sugar and fish sauce and stir until the sugar is dissolved. Season the broth to taste with salt and pepper.
Transfer to oven. Add the beef and any juices back to the pot with the chopped onion and carrot, cover, and transfer to the oven. Braised for 2.5 - 3 hours until the beef is very tender. Remove from the oven, discard the lemongrass and lime leaves, and rest 30 minutes before serving. Serve over steamed rice with cilantro, limes and chili oil on top.