It’s nuoc cham, not nuoc mam. Nuoc mam is fish sauce straight out of the bottle. It’s not something one makes at home as it requires fermentation and the process is both messy and smelly.
Nuoc mam cham, or nuoc cham for short, is a mixture of nuoc mam, citrus juice, sugar, garlic and chili. I understand that it is available in bottled form in some parts of the world, but know that it’s quite easy to make at home with pantry staples.

It was one of the most basic, and probably the most useful, recipes we learned at a farm-to-table cooking school in Cu Chi, an hour or so from the center of Ho Chi Minh City which I still prefer to call Saigon. After that trip, we were using nuoc cham with just about every dish at home. But, you know, as good and as versatile Vietnamese mixed fish sauce is, after a while, there is an unspoken urge to move on to other flavors and aromas. Then, after some time has passed, we go just back to it. It’s a cycle that gets repeated over and over.
The most recent recipe with nuoc cham

Chicken, shiitake and bok choy tips with nuoc cham – An easy but tasty stir fry that you can cook in a short time especially if you keep nuoc cham (Vietnamese mixed fish sauce) in stock. The sauce is easy to make and the formula is included in the recipe. Get the recipe.
More recipes with nuoc cham the blog archive

Pork patty spring rolls – Ground pork seasoned with Vietnamese mixed fish sauce is formed into patties, pan fried, combined with salad greens and herbs, and wrapped in rice paper. Get the recipe.

Vietnamese-style lemongrass pork and noodle salad – Lemongrass pork belly, noodles and fresh vegetables are tossed with Vietnamese mixed fish sauce to make a delicious one bowl meal. Get the recipe.

Asian cold noodle salad – Blanched ramen, cooked shrimps, lightly fried eryngii mushrooms, pickled vegetables and soy sauce quail eggs are drizzled with Vietnamese mixed fish sauce to make this Asian cold noodle salad. Get the recipe.

Shrimps, bean sprouts and watermelon salad – A light salad bursting with fruity flavors and the surprising tang and umami goodness of Vietnamese fish sauce. Get the recipe.

Pork and oyster mushrooms with Thai basil – Memories of Saigon. Pork and mushrooms are braised with lemongrass, garlic, ginger, chilies and fish sauce. Thai basil gives the dish a delightful aroma. Get the recipe.

Shrimp spring rolls – Our home version of a dish we learned to make at a cooking class in Vietnam, these shrimp spring rolls are traditionally served with greens to wrap them in before eating. Get the recipe.