A curry eaten out rarely tastes like the same dish cooked at home, even when the recipe is followed closely. The differences are structural and come from equipment and economics rather than hidden ingredients.
The burner is a different machine
Commercial ranges deliver far more heat than a domestic hob, and the pans are thin and shallow so that energy transfers quickly. A gravy can be brought up and reduced in minutes.
Rapid reduction concentrates flavour without the long, slow simmering that changes it in other ways. The finished sauce tastes fresher and more sharply defined.
High heat also produces browning at the pan edges that a lower flame never reaches, contributing a note home cooks often find missing.
Fat is used far more generously
Restaurant kitchens use considerably more oil or ghee than most people would at home, and much of it is added at the start rather than skimmed later.
Fat carries the spice compounds, coats the palate and gives the sauce its gloss and body. Reducing it changes both the mouthfeel and how strongly the spices register.
It also stabilises the sauce during holding, keeping it from separating between the moment it is finished and the moment it reaches the table.
Thickening is done with solids, not reduction
Ground cashew, melon seed, poppy seed or fried onion paste appear throughout restaurant gravies. Each thickens while adding richness, and each does so instantly.
Cream and butter perform the same role in the northern styles that became the standard export menu. The sauce reaches its final consistency without a long wait.
Home recipes often reduce instead, which takes longer and produces a sauce with more concentrated spice but less of the smooth body diners associate with eating out.
Seasoning is pitched for a single plate
A restaurant dish is built to make an impression across one serving, so salt, chilli, acid and sugar are all pushed further than in food cooked for a household every day.
Sweetness in particular is used deliberately to round the edges of chilli and acid. Its presence is one of the clearest markers of a commercially cooked gravy.
Domestic cooking is calibrated for repetition, and dishes eaten several times a week are naturally seasoned more moderately.
The finishing step happens off the recipe
Many kitchens finish a dish with cream, butter, crushed dried fenugreek leaf or a fresh spice mix stirred in at the last moment before it leaves the pass.
Those additions are rarely written down because they are adjustments made by feel, and they are the elements most often absent from a published version of the recipe.
Their common feature is that they are volatile or delicate, so they are added where nothing further will cook them away.