Kulfi and ice cream start from similar ingredients and end up as very different frozen desserts. The gap comes almost entirely from what happens during freezing rather than before it.
Churning is what makes ice cream light
An ice cream machine freezes and beats at the same time, folding air into the mixture continuously. That air can account for a substantial share of the finished volume.
The beating also keeps ice crystals small by breaking them up as they form. Fine crystals plus trapped air give the soft, scoopable texture people expect.
Kulfi skips this entirely. The mixture goes into molds and freezes undisturbed, so nothing is incorporated and nothing interrupts crystal growth.
Density changes how it eats
Without air, the same volume holds far more solids, which is why a small kulfi feels substantial. It is closer to a frozen block of concentrated milk than to a scoop.
It also melts more slowly, because a dense frozen mass has more material to warm through and less trapped air spreading heat inside it.
That slow melt suits the settings where kulfi is sold, since a portion survives being carried and eaten outdoors in a way a scoop would not.
The base is concentrated before freezing
Milk for kulfi is cooked down substantially before it is flavored and frozen, which raises the proportion of milk solids and lowers the water available to form ice.
Less free water means fewer large crystals even without churning, which is how an unchurned dessert avoids being unpleasantly icy.
Cooking also produces browned notes through reactions between milk sugars and proteins, giving kulfi a cooked-milk flavor that a fresh cream base does not have.
Molds are part of the method
Traditional conical metal molds are narrow, so the center freezes reasonably fast despite no agitation. A wide tub would freeze slowly enough to grow coarse crystals.
Metal also conducts far better than plastic, which shortens freezing time further. The shape and the material are doing work that a machine does elsewhere.
Vendors traditionally packed the filled molds into a pot of ice and salt, which drops the surrounding temperature below the freezing point of plain ice and speeds the process.
Making it in an American freezer
A home freezer runs warmer than commercial equipment and cycles through defrost, which encourages crystal growth. Small molds and a cold back corner both help.
Popsicle molds work in place of the traditional cones, and evaporated milk shortens the reduction step considerably for anyone unwilling to stand over a pot.
Ground nuts and starch are common additions for the same reason. Both bind free water that would otherwise become ice, which is a texture insurance policy rather than a flavoring.