Bun Thang Luon – Hung Yen’s Crispy Eel Noodle Soup with 20-Ingredient Broth

I – Kelly Thuy – first heard about bun thang luon from a friend who grew up in Hung Yen and had been living in Hanoi for years. Every weekend he drove 60km back to Hung Yen City just to eat a morning bowl and return. When I asked why he didn’t just eat Hanoi’s own bun thang nearby, he shook his head: “Completely different. The broth of Pho Hien bun thang luon cannot be replicated anywhere else.” After going there myself and tasting the first spoonful – a sweetness that was deep, clean and impossible to attribute to any single ingredient – I understood immediately what he meant. That was the sa sung.

— Kelly Thuy

What Is Bun Thang Luon?

Bun thang luon belongs to the “bun thang” family of Vietnamese noodle soups – characterised by multiple elaborately prepared toppings arranged carefully over fresh vermicelli before broth is ladled on. The Hung Yen version replaces shredded chicken (the standard central protein in Hanoi bun thang) with crispy turmeric-fried freshwater eel. That substitution – and the four-component broth that accompanies it – transforms the dish into something entirely independent.

Pho Hien – The Historical Context

Pho Hien – the area now comprising Lam Son and Hong Chau wards of Hung Yen City – was one of the most significant trading ports in northern Vietnam from the 16th to 18th centuries, when Chinese, Japanese, Dutch and English merchant ships anchored here to trade. A Vietnamese proverb captures its historical prestige: “First the Capital, second Pho Hien.”

The food culture of Hung Yen reflects this heritage of wealth and cosmopolitan exchange: elaborate preparation, diverse ingredients and generosity of serving. Bun thang luon – with its nearly 20 ingredients, skilled multi-step technique and hours of preparation – is the clearest expression of this culinary philosophy. This is not fast food. It is the food of a place that had time, resources and good ingredients, and knew how to use them.

The Four-Pillar Broth

The broth is what makes bun thang luon Hung Yen impossible to replicate elsewhere. The broth has crab, sea worms and dried shrimp. The important spice that needs to be added is shrimp paste which gives it a distinctive flavor. More specifically, the broth is built from four concurrent components:

The result is a broth with multi-layered sweetness that no single ingredient could produce alone. Creating a perfect bowl of bun thang luon requires numerous ingredients and meticulous preparation. It’s a labor-intensive process that demands patience and skill.

Ms Phuong, who has run a bun thang luon shop in Hung Yen City for many years, told me: “If you rush the broth, you ruin it. The sa sung needs long simmering to release its sweetness, the crab roe must be sautéed separately to develop its fragrance, the mushrooms must be fully soaked. Skip any step and the bowl is no longer bun thang luon from Pho Hien.” That is not modesty – it is a precise technical description.

— Kelly Thuy, field notes, Hung Yen

Sa Sung – The Secret Ingredient

Sa sung (sá sùng) is the ingredient that most defines the broth and is the least known outside specialist Vietnamese cooking circles.

Sa sung is the reason why the broth of bun thang luon Hung Yen has a sweetness that first-time eaters describe as “unattributable” – present and distinctive but impossible to pin to any single identifiable flavour. That is precisely the effect of high-quality sa sung in a well-made broth.

The Crispy Eel – Three-Stage Preparation

The eel meat is then marinated with turmeric, ginger, shallots, and salt to eliminate any fishy odor and enhance its color and flavor. After 15–20 minutes, the marinated eel is deep-fried with shallots until crispy. But before the marinating, there are two preliminary stages:

Stage 1 – Flame-singeing

The live eel is passed directly over flame until the outer mucus layer is burnt off and the eel is dead. This is a traditional northern Vietnamese technique for freshwater eel: more effective at removing fishiness than salt-rubbing or blanching, and produces firmer, more even meat texture.

Stage 2 – Boiling and shredding

The singed eel is boiled in lightly salted water, cooled, then shredded by hand into thin strips with all bones removed. This is the most labour-intensive step – small eels are particularly time-consuming to shred cleanly.

Stage 3 – Marinating and frying

Shredded eel meat is marinated with fresh turmeric, ginger, minced dried shallots and seasoning for 15–20 minutes. Fried shallots are made first in the oil for fragrance, then the eel goes in and fries over medium-high heat until golden-yellow and crispy throughout. Correctly fried: golden-yellow exterior, still moist inside, not hard or dry, fragrant with turmeric-ginger-shallot.

Full Ingredient List (~20 components)

Flavour and Texture Profile

Hung Yen’s bun thang luon attracts diners thanks to its visual harmony, with the white color of vermicelli, the brown color of eels, and the yellow color of eggs, plus the green color of herbs. The flavour matches the visual complexity:

What makes bun thang luon a memorable eating experience is not one dominant element but the simultaneous balance of all of them: crispy eel against clear sweet broth, soft pork roll against crispy pork belly, golden egg against green herbs. Each spoonful is a different configuration.

Bun Thang Luon vs Other Vietnamese Eel Noodle Dishes

How to Eat It

• Eat hot immediately – the crispy eel begins softening in the hot broth within minutes; this is the primary reason to eat without delay
• Taste the broth first – take one spoonful of broth before touching anything else; this is where the sa sung and crab complexity is most clearly present
• Add mam tom gradually – the shrimp paste side condiment is powerful; add a small amount at a time to deepen the flavour without overpowering the broth
• Morning eating – bun thang luon is a morning dish; most Hung Yen restaurants open from 6:30am and may sell out before 10am

Where to Eat It

In Hung Yen

• Pho Hien area – Lam Son and Hong Chau wards, Hung Yen City – bun thang luon is especially popular in the Pho Hien area, which spans the Lam Son and Hong Chau wards of Hung Yen City. The highest concentration of quality restaurants is here, with many family-run stalls that have been operating for decades. Most open from 6:30am and sell out between 9:30–10am.
• Hung Yen City centre – some restaurants in the broader city also serve bun thang luon, with variable quality.

From Hanoi

• Hung Yen City is approximately 60km (~1 hour by car) from central Hanoi. Many Hanoi residents make regular weekend morning trips specifically for this dish.
• Some Hanoi restaurants claim to serve bun thang luon Hung Yen-style, but the broth quality – which depends on high-grade sa sung and fresh sea crab – is rarely comparable to the source.

Price Reference

Nutritional Value

Estimated based on primary ingredients. No independently verified nutritional analysis of bun thang luon Hung Yen has been published. Freshwater eel is a high-protein food with notable omega-3 content; sa sung and sea crab contribute additional protein; pork belly contributes significant fat.

Frequently Asked Questions

What is bun thang luon?

The signature noodle soup of Pho Hien, Hung Yen: rice vermicelli in a broth made from sa sung (peanut worms), sea crab, dried shrimp and shiitake mushrooms; topped with crispy turmeric-fried freshwater eel, julienned pork roll, julienned fried egg, crispy pork belly and fresh herbs. ~20 total ingredients. Vietnam’s Top 100 Specialties 2020–2021.

How is it different from Hanoi bun thang?

Same structural concept (multiple toppings over vermicelli in clear broth), completely different ingredients: crispy eel vs shredded chicken as the central protein; sa sung-crab-shrimp-shiitake broth vs chicken stock; local Hung Yen vermicelli vs Hanoi vermicelli. The flavour profiles are entirely distinct.

What is sa sung?

Peanut worms (Sipuncula) – marine invertebrates from sea sand, most harvested in Quang Ninh. When dried and simmered, they produce a deep, clean, multi-layered umami sweetness often called “the sea’s natural MSG.” The defining ingredient of the bun thang luon broth.

Why is the eel flame-singed?

To burn off the outer mucus layer (removing fishiness more effectively than salting or blanching) and produce firmer, more evenly textured meat. A traditional northern Vietnamese technique for freshwater eel preparation.

Where to eat in Hung Yen?

Pho Hien area (Lam Son and Hong Chau wards, Hung Yen City), from 6:30am. Sells out before 10am. ~60km from Hanoi – approximately 1 hour by car.

Conclusion

Bun thang luon is what happens when a city with a centuries-long history of wealth, trade and culinary ambition decides to build a noodle soup. Twenty ingredients, each prepared separately according to its own technique, assembled into a bowl where the broth alone – made from sa sung, sea crab, dried shrimp and shiitake – is reason enough for a 60km drive before breakfast.

If you visit Hung Yen, arrive in Pho Hien before 8am. Sit down. Taste the broth first, on its own, before mixing anything. That first spoonful will tell you whether the sa sung is good. If it is, the rest of the bowl will follow.