ONE OF THE WORLD’S earliest monotheistic religions, Zoroastrianism arose out of a revelation to a prophet called Zarathustra in Avestan (a language now dead but still used in the recitations of Zoroastrian priests, learned by rote). He is believed to have been born in northeastern Iran or southwestern Afghanistan, and might have lived at any time between 6500 and 600 B.C.; the Roman historian Plutarch places him five millenniums before the Trojan War, while sacred texts cite a date two and a half centuries before the rise of Alexander the Great. Some scholars argue that Cyrus the Great, founder of the Achaemenid Empire in 550 B.C. — at that point the largest empire the world had ever seen — was a proto-Zoroastrian, although he did not impose the creed on those he conquered, which in retrospect may have been a mistake.

Today’s small community of Iranian Zoroastrians (around 14,000 as of 2011) welcomes converts, but Parsis do not — a pity, because there’s much that appeals about the religion right now, especially its tenets of tolerance and its early recognition of women as equal to men in moral agency, with a modern corollary of championing women’s education and pursuit of career. According to Zarathustra’s teachings, there is one god, Ahura Mazda, and two forces at war in the world, light and dark; the light, of God and of the illuminated human mind, is represented by the fire tended in Zoroastrian temples, never to be extinguished. The Zoroastrian mantra is manashni, gavashni, kunashni: good thoughts, good words, good deeds. But goodness does not require typical monastic asceticism. The opposite, in fact: Adherents must commit to engagement in the here and now, which includes embracing earthly delights, however fleeting.

The last of the Persian Zoroastrian empires fell to the Arab Caliphate in the seventh century A.D. Forced to choose between Islam and exile, many Zoroastrians fled, and several boats of refugees made it to the west coast of India in what is today the state of Gujarat. It is here that the story of the Parsis (the people from Pars, or Persia) begins, with food as an allegory for survival: As legend has it, the local Hindu ruler sent the newcomers a brimming cup of milk, to show that there was no room for more people in his kingdom; the Persians slipped in a spoonful of sugar, which disappeared, sweetening the milk without spilling it. This was a promise: They would assimilate and enrich India without altering its character.

Adaptation was key to their perseverance, and it remains the defining feature of Parsi food today — “a real magpie cuisine,” as King says, characterized by “gleeful borrowing.” From the Hindus: warm and musky spices and fondness for the seafood abundant along the Gujarati coast. From the Muslims, who took control of Gujarat at the end of the 13th century: an embrace of meat and viscera like lungs and heart, and the many ways to cook them. From the 16th-century Portuguese colonizers: the New World’s glory of chiles, potatoes and tomatoes. And from the British, who arrived in the 17th century: custard, soufflé and a somewhat stodgy fish-in-white-sauce recipe that Parsis improved with a slosh of vinegar.

The cooking also remains true to its ancient Persian roots, with liberal use of dried fruits and nuts and an emphasis on the interplay between sweet and sour. Unlike their first neighbors, the Gujaratis, who are predominantly vegetarians, Parsis are incorrigible carnivores and have no food restrictions. “We eat everything,” says Jeroo Mehta, 92, the Mumbai-based author of “101 Parsi Recipes” (1973) and an advocate for offal; her cookbook presents three elegant approaches to sheep’s brain. Animal protein is so fundamental to the Parsi diet that even during the holy month of Bahman, when Zoroastrians are supposed to abstain from meat, they’re permitted fish and eggs.