Sour Soup with Mud Carp and Sesbania Flowers, a Mekong Delta Flood-Season Specialty

Every year, from the 7th to the 10th lunar month, the Mekong Delta is replenished with silt as floodwaters from the upper Mekong River rush downstream and out to the sea. We people of the Mekong Delta call it the flood season.

The flood season brings the Mekong Delta not only rich silt but also local produce and rustic dishes that bear the unmistakable mark of the southern countryside, not least sour soup with mud carp and sesbania flowers.

This dish has become a classic of the Mekong Delta. What makes it special is that its ingredients are the signature produce of the region's flood season.

To cook an authentic bowl of Mekong Delta sour soup with mud carp and sesbania flowers, choosing the ingredients matters just as much.

To fully enjoy the rich, delicious flavor of mud carp, choose fish from early in the season, which locals call young mud carp. People in the delta catch them with nets, lift nets or cast nets; early in the season, hauls of young mud carp with glittering silver scales leap and splash.

Sesbania is a flower that only grows when floodwaters spill over the dikes and cover the fields of the Mekong Delta in white. Its deep yellow blossoms hang in clusters over the silt-laden water. Sesbania flowers are best before they open and must be picked very early in the morning.

Add some culantro (sawtooth herb), rice paddy herb, a few chilies and, above all, tamarind, which no sour soup can do without. I don't know how it is elsewhere, but in the Mekong Delta we usually use fresh tamarind, which keeps the broth clear and gives it a cleaner sourness.

Bring about half a pot of water to a boil, then add the tamarind. Mash it to release its sourness and season to taste. A pot of authentic Mekong Delta sour soup must balance sourness and sweetness against the heat of the chili. When the water boils again, add the mud carp. When it returns to a boil, taste and adjust the seasoning; a tip: season it slightly on the salty side, then add the sesbania flowers, turn off the heat and add all the remaining ingredients. The vegetables will tone down the saltiness, leaving your soup perfectly seasoned.

In a truly authentic, delicious bowl, the sesbania flowers should be just cooked, not mushy, and still a bright, eye-catching yellow. Add a little clear fish sauce with a few slices of chili and a bowl of hot rice, and you've tasted a true classic of the Mekong Delta.

Sour soup with mud carp and sesbania flowers , from the choice of ingredients to the way it is made, is as rustic, honest and simple as the people of the Mekong Delta. Simple and humble as it is, its flavor fills anyone far from home with a wistful longing, thanks to its harmony of sour, spicy, salty and sweet, the richness of the mud carp and the nutty taste of the sesbania flowers. Such homely deliciousness has even found its way into poetry:

         "Far away in the marshlands, eating sesbania flowers, I bow my head and miss my homeland"

If you ever have the chance, come to the Mekong Delta in the flood season and try this rustic sour soup that has become a "national dish" for the people of the delta.