Heat a deep sauté pan over medium-high heat. Add the beef and cook just until browned but still tender, about 1-2 minutes per side. Remove with a slotted spoon and set aside.
Add oil to the same pan. Stir in curry paste, garlic, and ginger. Cook 1–3 minutes until fragrant and slightly darkened.
Pour the coconut milk into the pan, mix with the paste, then bring the liquid to a soft boil, stirring to dissolve the paste.
Add the lime zest/juice, smashed lemongrass, fish sauce, and sweet Thai chili sauce (if using). Stir gently to combine.
Add the beef back to the pan, stir then lower heat to medium so it’s bubbling gently. Simmer for 5 minutes to build flavor. Taste and adjust if needed.
Lay the sliced bok choy and carrot over the curry. Pour broth over the top. Cover and simmer for 5 to 7 minutes, or until the vegetables are just tender and the sauce has slightly reduced.
Remove lemongrass and any other aromatics before serving.
Serve over rice or mixed with rice noodles. Spoon extra sauce over the top and garnish with green onions, Thai basil, and any optional garnishes.
