What Makes a Great Banh Mi?.

The bread decides it. A banh mi can have excellent pork, perfect pickles and house-made pâté, and if the baguette is dense or chewy it is a mediocre sandwich. Get the bread right and almost everything else has room to be merely good.

This is not the usual answer, but it is the one every Vietnamese bakery is organised around — which is why the best banh mi in most cities is sold by a place that bakes rather than by a place that cooks.

1. The bread: thin crust, hollow inside

A Vietnamese baguette is not a French one. It is made with rice flour alongside wheat, which produces a crust that shatters into flakes and a crumb that is airy to the point of being nearly hollow. The whole loaf should feel light for its size.

What to look for:

• It makes a mess. Crust flakes on the counter are a good sign.
• It gives immediately. A sandwich you have to tear at has too much crumb, and you will end up eating mostly bread.
• It was warmed. Most bakeries flash their rolls in an oven before filling. A cold roll from a bag is the single most common failure.

If the bread is the same as the one under the deli's Italian sub, you are not eating a banh mi in any meaningful sense.

2. Pâté and mayonnaise, both actually present

The base layer is pork liver pâté on one side and mayonnaise — often house-made, sometimes enriched with egg yolk — on the other. Together they line the bread, keep it from going soggy, and supply the savoury weight that the vegetables cut against.

Shops that skip the pâté are usually doing it to make the sandwich more approachable, and the result tastes flat in a way most people cannot identify. If you have found banh mi underwhelming, a missing pâté is the likeliest reason.

3. Pickles with bite

Đồ chua — daikon and carrot pickled in vinegar, sugar and salt — supplies the acid. They should be crisp and cut into matchsticks, and they should taste sour first and sweet second. Soft pickles mean they sat too long; cloyingly sweet ones mean the shop is compensating for something.

Alongside them: cucumber batons for water and crunch, coriander sprigs, and sliced chilli. The chilli should be optional and it should be fresh, not from a jar.

4. The filling, in proportion

The classic is thịt nguội or đặc biệt: a combination of cold cuts — Vietnamese ham, headcheese, pork roll — layered thin. Grilled pork (thịt nướng), lemongrass chicken, grilled beef, sardines in tomato sauce and tofu are all standard variations.

Proportion is where American versions most often go wrong. A banh mi is not a meat sandwich with vegetables on it; it is closer to balanced. When the filling is piled high, the bread compresses, the pickles get lost, and you lose the thing that made the sandwich distinctive in the first place.

5. Assembly and timing

It should be built to order and eaten within the hour. Pickles release liquid, mayonnaise softens crumb, and a banh mi that has been sitting wrapped since morning has a soft crust no matter how good the bakery is.

A good sign at the counter: a queue, a stack of rolls that visibly depletes, and someone toasting bread continuously rather than in batches.

What a great one tastes like

Crackle first, then richness from pâté and mayonnaise, then sourness from the pickles, then the meat, then a slow build of chilli. Five distinct things in sequence, in a sandwich that costs less than most cups of coffee. When one of them is missing you notice, even if you cannot say which.

Where to eat one in the South Bay

San Jose has an unusual concentration of Vietnamese bakeries, which means the bread problem that limits banh mi in most American cities largely does not apply here. Forkelo ranks the best banh mi in the South Bay on evidence about the sandwich itself, with a separate list for San Jose.

For what else to order once you are in the door, read what bún bò Huế is or what cơm tấm is, or start with the pho ranking.