The custom of storing winter snow and ice in pits or insulated buildings in order to relieve the heat of summer appears to go back to the ancient civilizations of Mesopotamia and China as well as those of Greece and Rome, in whose marketplaces snow was sold. In Sicily, Etna itself offered not only an abundant supply of snow but a means of preserving it: the mountain is a natural refrigerator, spitting out volcanic ash that falls in an insulating blanket over the snow gathered in its crevices. Man improved on nature, and by the mid-18th century Sicilians were shoveling snow into underground caverns on the volcano and compressing it into large blocks—which, when wrapped in straw and burlap, could be stored at length and even transported. The bishop of Catania, close to Etna's slopes, once sent a boatload of snow all the way to Rome as a present for the pope.

Sicily's desire for ice continued unabated during the waves of invasion and conquest to which the island was prey. Greek and Roman colonists cooled their wine with Etna's snow. Arabs, who arrived in the 10th century bringing cane sugar and citrus fruits, put snow in their lemonade. In the 11th century the Normans landed, and Roger II, Sicily's first Norman king, supposedly granted the bishop of Cefalu, near Palermo, the exclusive right to sell snow from the mountains in the west, at the same time that the bishop of Catania was establishing a monopoly over the snows of Etna in the east—lucrative trades that flourished in the following centuries. Sicily was a land ripe for the invention of ice cream, possessed of both the raw materials and the appetite.

But when and where, exactly, did naturally iced water become man-made water ice? Food historians now believe that it was probably sometime around 1650 and someplace in Italy that the ancient love of drinks cooled by natural snow or ice met the scientific knowledge of the endothermic effect—the rule of physics that makes it possible to freeze a liquid by conduction, surrounding it with a mixture of ice and salt that, as it melts, reaches temperatures well below the freezing point of water alone.

Scientists and philosophers had been experimenting with this technique for a long, long time; descriptions of the process can be found in a fourth-century Indian poem, an Arab treatise of the 13th century, and the Magia Naturalis of Giambattista della Porta, published in Italy in 1589. Determining the moment at which the salt-and-ice technique passed from the laboratory to the kitchen is complicated by vocabulary: the terms ice, glace, and gelato have long been used interchangeably, in their respective languages, to denote both something naturally frozen and an artificially frozen dessert.

Whoever it was that came up with frozen sweets, the Sicilians knew a good thing when they tasted it. By the late 1600s, Sicilian ice cream makers were famous throughout Italy, creating granitas (granular concoctions of fruit and ice), sorbetti (ices churned smooth during freezing), and sorbetti con crema (ices with milk added—forerunners of gelato) for aristocratic households.

Sicilians took their ice cream very seriously, at all levels of society. In northern Italy, ices remained the preserve of the sick or the wealthy until the late 19th century, owing to the cost and limited availability of ice and other ingredients. But in Sicily even peasants considered ices their due. William Irvine, an English gentleman visiting there in the early 1800s, marveled that "wretches whose rags have scarse adhesion enough to hang upon their bodies, yet find a baioc [a coin worth less than a penny] to spend in the ice shop". The lackadaisical Sicilian legislators may have been described as an "ice cream and sorbet parliament" by King Vittorio Amedeo II in the 1700s, but these were men who knew their priorities: when in 1774 Palermo's supply of snow gave out, the parliament dispatched armed dragoons to Etna to procure more. The demand for snow was insatiable. It is said that during a ball given in 1799, likely for the Bourbon king Ferdinand and his wife, Maria Carolina, such a quantity of ices was served that their production required 11,000 pounds of snow.

Both the Sicilians' centuries-old skill at making ice cream and their enduring passion for the results are evident at any number of Sicilian gelaterie, or ice cream shops, at almost any hour of the day or night. Walk into Palermo's Gelateria Stancampiano, for instance, and you'll find 48 varieties of fine gelato and sorbetto doled out long into the night—especially to teenagers, who clutter up the sidewalk outside until 3 a.m., leaning against parked motor scooters and devouring their dripping choices.

Does this kind of passion for ice cream have something to do with the collective memory of preserving and using ice, or with the warm climate, or perhaps simply with the deliciousness of the ice cream itself? It was not until I started talking with Angelo La Mattina, who makes marvelous ice cream in a shop called Gelato 2, around the corner from my Palermo apartment building, that I began to understand the special bond that ties Sicilians to their frozen sweets.

First of all, he told me, the gelato in Sicily is different from that found in the rest of Italy. Unlike most mainland ice cream, Sicilian gelato rarely contains eggs or cream. Instead, the base, known as crema rinforzata, is a rather liquid version of blancmange, a sweet pudding of milk thickened with corn (or rice) starch. The resulting ice cream has a "warmer" feel than sorbetto or granita, according to La Mattina, yet is lighter than its eggy northern counterparts—and, in a region where ice cream was long considered a birthright but eggs a luxury, it was less expensive to produce.

Sicily probably owes its crema rinforzata both to its Arab conquerors and to some four centuries of Spanish domination that ended in 1713. Blancmange made in this manner is still eaten across the Arab world, where it is known as muhallabia. It was called biancomangiare alla catalana (blancmange Catalan style) in the cookbooks of the Italian Renaissance and was served in a cradle of snow at the great banquets of the Medici court. Biancomangiare remains popular in Sicily, where it is made with cow's milk or with almond "milk" (water in which crushed almonds have been soaked).

La Mattina also reminded me of all the appealing ways in which Sicilians serve their gelato. A favorite breakfast is gelato con brioscia, a scoop of freshly made ice cream (or, in summer, granita) in a slightly sweet roll. The gelato used for this purpose is called spongato and owes its extraordinary texture and smoothness to the fact that it is never chilled long enough to harden fully. For my children, who would arrive on the early-morning train on vacation from mainland universities, hazelnut gelato in a brioche was always the first taste of home. Their friends from northern Italy, my daughter tells me, have a hard time eating gelato con brioscia, for it's something of an art: too much pressure on the bun, and the ice cream ends up on the floor. One must rotate the brioche smoothly, alternating between a long, slow lick of ice cream and a nibble along the edges of the bread. The goal is to come out even at the end.

Ice cream eating as an event, involving leisurely consumption at a table, takes place in the afternoon or evening in Sicily (though brioche addicts continue straight through the day). Popular choices are spongato in a cup and the pezzo duro (hard piece), a slice of a solidly frozen ice cream brick, roll, or bombe. In Palermo this might mean a portion of a giardinetto, a rectangle of lemon and strawberry sorbetti covered with tiny cubes of candied citron, or a wedge of cassata gelata, a bombe layered with several flavors of ice cream and a mix of whipped cream, citron, and chocolate bits. In Catania, the pezzo duro is likely to be more elaborate—for instance, the schiumone (a bombe with a zabaglione center) or the misto Umberto (constructed of a chocolate ice cream exterior with pistachio and vanilla ice creams inside, layered with sponge cake and candied cherries).

The influence of French chefs, who were in vogue among the noble households of the 19th century, can still be seen in the semifreddo di mandorla, a loaf of semifrozen almond-brittle custard that has eggs and cream galore. A favorite in fancy restaurants, this semifreddo is usually accompanied by chocolate sauce, but in Palermo the private club Circolo Unione serves it with heated bitter-orange preserves—a truly Sicilian touch to tame the foreign beast.

Ice cream has only recently become a subject for study as well as indulgence, so who knows? Ancient records and family archives may yet prove what I have long suspected: that ice cream was invented not in mainland Italy but in Sicily! But whether Sicilians invented ice cream or only adopted it, their genius for making and enjoying it is alive, there to be tasted in each irresistible spoonful of gelato.