In a large pot, heat some oil over medium-high heat. Add the sliced beef and cook until browned. Remove the beef from the pot and set aside.
In the same pot, add the onion, garlic, bell pepper, and carrot. Cook until the vegetables are softened, about 5 minutes.
Add the curry powder to the pot and stir to coat the vegetables.
Pour in the beef or vegetable broth and coconut milk. Bring the mixture to a simmer.
Add the bean thread noodles to the pot and cook for about 5 minutes, or until the noodles are tender.
Return the cooked beef to the pot and season with salt and pepper to taste.
Serve the soup hot, garnished with chopped cilantro.
Enjoy!