A dish that moves to another country almost never arrives unchanged. The alterations follow patterns consistent enough to be predicted before tasting.
Substitution starts with what is missing
The first changes come from ingredients that simply are not available, or are available only at a cost the dish cannot carry.
Cooks substitute by function rather than by identity, replacing a sour fruit with a sour liquid, a specific green with whichever local leaf wilts similarly, or a regional chilli with whatever delivers comparable heat at the right price.
Those substitutions accumulate, and after several rounds of them the dish shares a name and a broad structure with the original while sharing very few of its actual components.
The palate of the destination pulls hard
Diners in a new market bring expectations formed elsewhere, and dishes that violate them too sharply sell poorly and disappear.
Chilli heat is usually the first thing moderated, followed by fermentation and bitterness, both of which are acquired tastes with narrow initial audiences and no obvious appeal to a first-time diner.
Sweetness typically moves upward, since sweetness is broadly acceptable across palates and reliably softens the elements a new audience finds challenging, which makes it the cheapest available adjustment.
Restaurant economics reshape the format
A dish that took a household half a day cannot be cooked to order, so it is broken into components prepared in advance and finished quickly.
That restructuring changes texture and depth even when every ingredient is correct, because time in the pot was itself an ingredient.
Portion size and plating shift too, since a dish served as one of many at home becomes a standalone order abroad.
The migrant version becomes its own tradition
After a generation the adapted dish stops being an approximation and becomes a genuine local speciality with its own standards and defenders.
Diners who encounter the adapted version first will find the original unfamiliar rather than authentic, which is a matter of sequence rather than error.
Several dishes now regarded as national icons in their adopted countries began exactly this way and have no exact counterpart at their source.
Reverse migration closes the loop
Adapted versions sometimes travel back, arriving in the original country as a novelty rather than as a correction.
Restaurants there may serve both versions, marketed differently, with the returned one positioned as foreign food.
The result is two living versions of the same dish, each authentic to a place, which makes arguments about which is correct largely unresolvable.