1. Prepare the Beef

To start, thinly slice the beef into bite-sized strips. If your beef is difficult to slice, freeze it for 30-45 minutes before slicing to make it easier to cut. Choose a tender cut of beef like sirloin or flank steak for the best texture, but any thinly sliced beef will work in this recipe.

Heat 1 tablespoon of vegetable oil in a large pot or Dutch oven over medium-high heat. Add the beef to the pot in batches, being careful not to overcrowd the pan. Brown the beef for 3-4 minutes, stirring occasionally to ensure it cooks evenly on all sides. Once browned, remove the beef from the pot and set it aside.

2. Sauté the Aromatics

In the same pot, add the remaining 1 tablespoon of vegetable oil. Once hot, add the sliced onion and sauté for 3-4 minutes, or until the onion becomes soft and translucent. Add the minced garlic and ginger and cook for another minute, allowing the flavors to bloom. These aromatics form the base of your soup’s rich, flavorful broth.

3. Add the Spices and Seasonings

Once the onions are softened and fragrant, add the chili paste, soy sauce, fish sauce (if using), and ground coriander and cumin. Stir to combine and let the spices toast in the hot oil for 1-2 minutes. This step intensifies the flavors and helps bring out the heat and depth in the broth.

For additional heat, you can add chili flakes to taste. The chili paste and chili flakes will provide the spicy kick, but feel free to adjust the amount based on your personal preference.

4. Add the Broth and Simmer

Pour in the beef broth and water, stirring to combine with the spices. Add the sugar, which helps balance the heat and enhances the flavors in the broth. If you prefer a slightly tangy broth, add the rice vinegar to balance the spice with some acidity.

Bring the soup to a boil over medium-high heat. Once boiling, reduce the heat to low and let it simmer for 30-40 minutes. This simmering time allows the flavors to meld together, creating a rich and aromatic broth.

5. Cook the Noodles

While the soup is simmering, cook the noodles according to the package instructions. If you’re using rice noodles, they typically take only 3-4 minutes to cook, so keep an eye on them. Once cooked, drain the noodles and set them aside.

For the best texture, it’s recommended to cook the noodles separately so they don’t become too soft or soggy in the broth. This will allow the noodles to retain their chewiness and make the soup even more enjoyable.

6. Add the Vegetables

Once the broth has simmered and the flavors have developed, add the fresh bok choy or spinach to the soup. These greens add color and nutrition, and they cook quickly in the hot broth, wilting down in just a few minutes.

Stir the soup to incorporate the vegetables, allowing them to soften in the broth for 2-3 minutes. If you prefer your greens to have more bite, you can cook them for a shorter period.

7. Return the Beef to the Soup

Now, return the browned beef to the pot, stirring to combine with the broth and vegetables. Let the soup simmer for an additional 5-7 minutes to heat the beef through. If you prefer a thicker broth, you can use a slotted spoon to remove some of the vegetables and beef and then reduce the liquid further by simmering it uncovered for a few extra minutes.

8. Assemble the Soup

To serve, divide the cooked noodles among bowls. Ladle the hot broth, beef, and vegetables over the noodles. Garnish the soup with a drizzle of sesame oil, fresh cilantro, and sliced chili peppers for an extra kick of heat. Serve with lime wedges on the side, which add a fresh, tangy contrast to the richness of the broth.