ARRIETA, Spain — Making his way down a row of pea plants, Iker Villasana Hernaez, a Basque farmer, leans down to feel each pod individually before deciding whether it is ready to pick.

If the peas inside feel slightly hard, "best to leave it for one more day," he said. "It's really all about the perfect timing."

Such harvesting is backbreaking work, particularly compared with the tractor-driven, industrial farming commonly used for peas. But the reward is that this pea, called the "guisante lágrima," or "tear pea," because of its small size and shape, has also become known as "green caviar" among Spain[1]'s flourishing community of top chefs.

It is a vegetable so highly prized that, once it is shelled, its value reaches around 200 euros a kilogram, or roughly $100 a pound. That places it in the ranks of the world's exquisitely priced edible plants and vegetables. (The hop shoot sells for as much as €1,000 a kilo.)

"This is an extraordinary and incredibly seasonal produce," said Joan Roca, the Catalan chef whose family-run restaurant, El Celler de Can Roca[2], has been rated the best in the world. "This pea really is like a grain of caviar that explodes in the mouth."

But the tear pea also exemplifies the symbiotic relationship between Spain's leading chefs and local farmers, and how it is helping revive some rare and nearly forgotten indigenous produce.

In fact, Mr. Villasana Hernaez grows everything exclusively for Josean Alija, the chef of Nerua[3], a restaurant in Bilbao's Guggenheim Museum, which has been awarded one Michelin star.

Nerua's ascendancy allowed Mr. Villasana Hernaez to turn his farming hobby into a full-time job and "a nonstop experiment with weird and wonderful products."

Mr. Villasana Hernaez, 39, said he was always attracted by the farmland and planted an orchard as a youngster next to his family's holiday home.

Five years ago, after his mother died, he made a more radical lifestyle change and walked away from the family-owned driving school where he had taught.

He decided to start "growing things that others didn't." For the first two years, he sold as many as 20 varieties of pumpkins and other produce at specialty food markets and local fairs, until a friend put him in touch with Mr. Alija, who offered him a chance to break through as a top restaurant supplier.

Today, Mr. Villasana Hernaez estimated that he is among a dozen producers of tear peas around the Basque Country.

"Gastronomy has brought back value to a type of ecological agriculture that was being lost, and it is encouraging more young people to become farmers and make nature their work office," he said.

Mr. Villasana Hernaez sows his peas in January and harvests them about four months later. He also grows about 30 other vegetables or herbs for Mr. Alija, from the autochthonous to the exotic.

In addition to the peas, he harvests "baby" versions of other vegetables, including undersized pumpkins, carrots, and six varieties of eggplants, originally from countries like Turkey, Italy and Japan. His herbs include huauzontle from Mexico and jambu, also called toothache plant, from Brazil.

The tear pea is expensive because of its unpredictable and short harvest, the intensive labor it requires, and the need to transport it quickly from the orchard to the kitchen.

During the spring harvest, Mr. Villasana Hernaez picks the peas early in the morning to avoid exposing them to strong sunlight. Then he drives 20 minutes from his hillside greenhouse to Nerua's kitchen in Bilbao, where eight of Mr. Alija's assistants spend about 45 minutes delicately shelling them.

This is followed by a second selection process, as some misshaped or larger peas get discarded or are turned into a fried appetizer dish. The peas are cooked only for seconds, using one of three different techniques, depending on what Mr. Alija is preparing.

The tear pea's skin is thin and fibrous, requiring it to be handled delicately. But it is also what helps create the sensation of an "explosion" in the mouth when the skin is burst and the sap and sugars are released.

Despite its sweetness, the pea also has a slightly salty taste, which Mr. Alija attributes to the sea winds that sweep across the coastal farmland of the Basque Country. The tear pea is tasty even raw, but gains flavor when it is slightly steamed or grilled because the smoke adds "a spicy touch," Mr. Alija said.

Last year, he combined the peas with egg yolk and vanilla, and this spring he served them with an olive oil ice cream and grapes. For 2017, Mr. Alija is planning to add Swiss chard juice and chili pepper to the peas.

However the tear peas are served, "it is all in the moment," Mr. Alija said.

"Two days of keeping means losing 60 percent of its quality," he added, unlike truffles and other gourmet produce that keep longer and travel more easily.

In fact, the sugar of the tear pea begins to transform so quickly into starch right after it is picked that it would be challenging to deliver unaltered even to Madrid, about 250 miles away, according to Mr. Villasana Hernaez.

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Mr. Roca, the chef of El Celler, said he discovered the tear pea in the Basque Country, and persuaded his local Catalan producer to start growing his own version, which "is a bit different, but has the same taste and gives the same sensation."

"The development of this pea is a fantastic example of the dialogue and relationship between the chef and the local producer," Mr. Roca said. "Even if you can't expect people on the street to pay such a high price for peas, I think gastronomy is the springboard to show just what our orchard can yield."

In turn, he added, being able to produce something special like tear peas "brings prestige to a farming region, which will trickle back down to ordinary consumers."

Not every Spanish chef, however, is as enthralled.

"Everybody suddenly seems to be using the tear pea, but I think it's a bit of a fashion," said Óscar Velasco, who runs Santceloni[4], a restaurant in Madrid that has been awarded two Michelin stars. "For me, the texture of the tear pea somewhat lacks crunchiness because it is just too small."

Instead, Mr. Velasco uses a sweeter and larger pea grown in Maresme, in Catalonia.

Even if all his colleagues have not been won over by his favorite pea, Mr. Alija seems to value the tear pea as much for how it bonds him to Mr. Villasana Hernaez, his fellow Basque and farmer, as for its flavor.

"The essence and soul of high gastronomy is in the local," he said.