Mentions of mother sauces tend to trigger notions of béchamel, espagnole and hollandaise, heavy with flavor, flour and centuries of exacting French technique. It’s a different world from the one Peter Franklin conjures when he uses the term while giving me a tasting tour of Vietnamese cooking.

Because in the kitchen of Ănăn Saigon—his multistory warren of sleekly modern restaurants and bars off Ho Chi Minh City’s Tôn Thất Đạm street market—heft gives way to herbs, stocks stand down for savory soy sauce, roux is replaced by bright acids, and boldly delicious fish sauce appears almost everywhere. This is cooking that is lighter, brighter and more vibrant.

Yet it does owe something to the French, who controlled Vietnam for decades and left behind their tradition of flavoring with sauces. “Most dishes, there’s not much flavor beyond the freshness of the herbs and vegetables,” Franklin explains of Vietnamese cuisine. “Most of the flavor comes from the sauces.”

Some are as simple as water, sugar and fish sauce cooked to a deep caramel. Others are more bracing, blending shallots, lime juice, sugar, garlic and—of course—fish sauce. One of my favorites is mỡ hành, or scallion oil. At its most basic, it is simply hot oil poured over chopped fresh scallions, the heat gently tenderizing the greens, the fat drawing out their flavor.

I’d encountered it at multiple meals. Spooned over grilled pork skewers. Blended with soy sauce for a simple dressing for roasted eggplant. Sweetened with a touch of sugar and spiked with grated fresh ginger for a spring roll dipping sauce. Each time, it tastes fresh, boisterous and savory.

When Franklin prepares it for me, the oil blisters and sizzles as it hits a mound of scallions and black pepper, his open kitchen immediately filling with sweet onion flavor. He adds ginger and fish sauce, and suddenly the aroma of green is matched by savory, sharp flavors. I take a taste and immediately am seduced.

At Milk Street, it was a simple matter to replicate Franklin’s version. And at his urging, we did as the Vietnamese do—happily pairing it with most anything.