Bun Bo Hue Spice Mix: Make the Fragrant Chili Oil

Bun bo Hue spice mix is a fragrant, spicy seasoning used in bun bo Hue, the beef-and-pork noodle soup from central Vietnam. This recipe makes a concentrated lemongrass, chili, and annatto oil that seasons broth or can be adjusted at the table; regional and household versions vary in heat and aromatics.

Ingredients

3 tablespoons (45 ml) neutral oil, such as canola or sunflower
2 tablespoons (30 ml) annatto seeds
2 tablespoons (30 ml) finely minced lemongrass, tender inner stalks only
2 tablespoons (18 g) finely minced shallot
1 tablespoon (9 g) finely minced garlic
1 tablespoon (7 g) Korean chili flakes (gochugaru), or mild red pepper flakes
1 teaspoon (2 g) ground turmeric
1 teaspoon (5 g) fine salt
1 teaspoon (5 g) fish sauce
½ teaspoon (1 g) freshly ground black pepper
1–2 teaspoons (5–10 ml) chili oil or extra neutral oil, optional, for more heat

Instructions

Prepare the aromatics before heating the oil. Remove any dry outer layers from the lemongrass, then mince the tender center very finely so it softens quickly. Mince the shallot and garlic separately. Keep the chili flakes, turmeric, salt, fish sauce, and pepper within reach; the spice mixture cooks quickly once added.
Put the neutral oil and annatto seeds in a small, light-colored saucepan. Set it over low heat and warm gently for 3–5 minutes, stirring now and then, until the oil turns a deep orange-red. Do not let the seeds smoke or turn black, which can make the oil bitter. Remove the pan from the heat and strain the oil through a fine-mesh sieve into a heatproof bowl. Discard the seeds.
Return the colored oil to the saucepan and set it over medium-low heat. Add the lemongrass and shallot. Cook for 3–4 minutes, stirring often, until softened and fragrant but not browned. If the mixture starts to sizzle aggressively or catch on the bottom, lower the heat.
Stir in the garlic and cook for about 30 seconds, just until fragrant. Add the chili flakes and turmeric, then stir continuously for 30–45 seconds. Keep the heat low: dried chili and garlic scorch easily, and burnt spices taste harsh rather than warm and aromatic.
Turn off the heat. Stir in the salt, fish sauce, and black pepper. Taste a small amount once cool enough; it should be salty and aromatic because it will season a larger pot of broth. For a hotter mix, stir in chili oil a little at a time. Let cool before transferring to a clean container.
To season soup, start with 1 tablespoon (about 15 ml) per 4 cups (950 ml) of hot broth, stir, and taste. Add more gradually to suit the broth and your preferred heat. This is a seasoning oil, not a complete bun bo Hue soup; the broth still needs its own salt, fish sauce, and other seasonings.

Tips

Use gentle heat. Annatto colors oil readily, while burnt seeds, garlic, or chili can leave an unpleasant bitterness. If the annatto oil turns dark brown or smells burnt, it is better to start that step again.
Choose the chili to suit the dish. Gochugaru gives a fruity, mild-to-medium warmth and vivid color. Regular red pepper flakes are sharper and may contain seeds, so begin with less if you are unsure. Add heat to the finished broth a little at a time.
Make the lemongrass fine. Large woody pieces stay chewy. If fresh lemongrass is unavailable, use 1 teaspoon (2 g) dried lemongrass powder in place of the minced fresh lemongrass; the flavor will be less fresh and citrusy. Stir it in with the other ground spices.
Keep the oil from splattering. Dry the saucepan and aromatics well, and add minced ingredients carefully. Fish sauce goes in off the heat to reduce sputtering and preserve its aroma.

Serving Suggestions

For bun bo Hue, stir the mix into beef or pork broth while it is hot, then adjust salt and fish sauce separately. Serve the soup with rice vermicelli, sliced cooked beef or pork, and optional toppings such as sliced onion, scallions, cilantro, lime wedges, and fresh herbs. Bean sprouts and banana blossom are also common accompaniments where available. Because the mix is concentrated, add it gradually rather than pouring the whole batch into one pot.

You can also spoon a little over plain rice noodles, use it to flavor a quick noodle broth, or mix a teaspoon into a bowl of soup at the table. Keep a clean spoon for serving so broth or food does not get into the storage container.

Variations

More traditional lemongrass character: Increase fresh minced lemongrass to 3 tablespoons (45 ml), keeping it finely chopped. It will make the mix more citrusy and textured.

Milder seasoning: Use 1 teaspoon (3 g) chili flakes and omit the optional chili oil. The annatto still gives the mix its red-orange color without requiring extra chili heat.

Without annatto seeds: Replace the annatto oil step with the same amount of neutral oil. The seasoning will taste similar but lack the characteristic orange-red hue. A small pinch of paprika may add color, though it changes the flavor slightly.

Lower-salt option: Omit the salt and add it to the broth only after tasting. Keep the fish sauce modest as well, especially if the broth or other soup components are already seasoned.

Storage and Reheating

Cool the seasoning promptly and refrigerate it in a clean, airtight container within 2 hours of cooking. Use within 4 days for best quality. For longer storage, freeze in small portions for up to 2 months; thaw in the refrigerator. Do not store this homemade mixture at room temperature or attempt to can it. Reheat only the portion needed in a small pan over low heat, or stir it directly into hot broth. If reheating leftover soup, bring it to 165°F (74°C), the USDA FSIS safe minimum for leftovers.

Frequently Asked Questions

Is bun bo Hue spice mix the same as bun bo Hue paste?
This recipe is an oil-based seasoning mix, not a thick commercial paste. Some packaged products include more salt, shrimp paste, or other seasonings, so their flavor and strength differ. Start with a small amount when using this homemade mix in broth.

Can I make it without annatto?
Yes. Use neutral oil and continue with the aromatics as directed. Annatto mainly provides the signature red-orange color and a subtle earthy note; without it, the mix will look paler.

How much spice mix should I use in a pot of soup?
Begin with 1 tablespoon (15 ml) for every 4 cups (950 ml) of broth, then taste. Broths vary in saltiness and strength, so add more in small increments rather than relying on a fixed amount for every pot.

Can I use powdered lemongrass?
Yes. Use 1 teaspoon (2 g) dried lemongrass powder instead of 2 tablespoons of fresh minced lemongrass, and add it with the chili and turmeric. It is convenient, but its aroma is less bright and fresh.

Why did my spice mix turn bitter?
The most common cause is overheating annatto seeds, garlic, or chili. Keep the oil over low to medium-low heat, stir continuously after adding ground spices, and remove the pan from the heat as soon as the aromatics smell fragrant.

Can I make the mix ahead?
Yes. Prepare it up to 4 days ahead and refrigerate promptly in a sealed container. For the freshest aroma, add it to broth shortly before serving rather than simmering the seasoning oil for a long time.

More recipes to cook

Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

Spotted an error? Tell us and we will correct it (corrections policy).