Explainer | What makes the best Vietnamese nuoc cham? Banh xeo, bun chay, ban hoi and spring rolls are great summer dishes – but wouldn’t be the same without the sweet and sour dipping sauce

Vietnamese food is the go-to for those hot summer months when people are searching for a light meal packed with fresh herbs and vegetables, accompanied by that distinctive jar of orangey, sweet and sour dipping sauce.

Whether crispy banh xeo (Vietnamese crepes), bun chay (noodle salad), banh hoi (rice vermicelli bundles), spring rolls or even summer rolls, none of these dishes are complete without nuoc cham. And there’s more to the quintessential dipping sauce than what meets the eye.

“It is the spirit of Vietnamese cuisine,” declares Giang Muoi, executive chef of An Nam restaurants in Hong Kong. “If you want to test if a Vietnamese chef knows their stuff, then you don’t test them by anything else, just how they make the nuoc cham is enough.”

So what qualifies as a good dipping sauce?

“You won’t be able to stop eating,” says Giang. “The sweet, sour and umami flavours should whet your appetite and have you craving for more. I always include some in my staff meals and the girls always ask for seconds.”

The secret to making a good dipping sauce comes as no surprise: it’s all about the ingredients. “Never use vinegar,” insists chef Giang. “A lot of restaurants keep the food cost down by using vinegar instead of lime juice, but that is a huge mistake. Vinegar strips off the palate and makes all food taste bland. This creates the opposite effect of what nuoc cham should do; instead of increasing your appetite, it limits your enjoyment of the dish.”

And it has to be made with the finest quality ingredients your money can buy. “Always use the best fish sauce you can get your hands on. In Vietnam, the best fish sauce comes from Phu Quoc where the waters are clear and the fish sauce is made with fresh fish,” says Giang.