Decades later he sees it as the "miracle" grain that could replace quinoa and transform the economy of the Sahel.
Fonio has been grown for over 5,000 years and is possibly the oldest cultivated cereal in Africa. The gluten-free grain, native to Thiam's birth country, Senegal, has been touted as the next quinoa.
"It is nutritious, particularly rich in methionine and cysteine, two amino acids that are deficient in most other major grains: barley, rice or wheat to name a few," the chef said of fonio at the recently concluded TEDGlobal Conference in Tanzania.
And it is from exporting this grain that he believes the Sahel can turn its economy around.
The mystery of a grain
Years ago while doing research for his cookbook, Thiam was reintroduced to fonio, the grain he knew from childhood.
He would later learn that everywhere fonio was grown, it was shrouded in myths and superstitious beliefs.
"In Casamance, Senegal (where my parents are from), growing fonio around one's compound is believed to keep away the evil eye," he said.
His study led him further down a rabbit hole of discovery.
Natives of Dogon in Mali believe it is "the seed of the universe" where the Earth sprouted, while in ancient Egypt the grain was found in the pyramids' burial grounds.
"I became more interested in this grain that was deemed worth taking to the afterlife by early Egyptians," he said.
Rich grain, poor land
Fonio is cultivated in Kédougou, a place Thiam describes as "one of the poorest regions of Senegal."
"Because of desertification and lack of job prospects, much of Kédougou's young population has left. They chose the deadly path of migration in search of 'better' opportunities. Often, they risk their lives trying to reach Europe," he said in his TEDtalk.
For him, exporting the resilient fonio, which "thrives where nothing else will grow," might be the answer to the looming poverty.
"Although we are still at an early stage of development, we are collaborating with an NGO called SOS Sahel to recruit, train and equip the youths throughout the Sahel region, including Kédougou. The youths are happy to have the opportunity of a paying job," he later told CNN.
One grain, many possibilities
Despite the great potential fonio has, he says there is a lot of work to be done in changing Senegalese locals' perception of it as "country-people" food.
In an effort to upgrade its status and share it with the world as a "world-class crop," Thiam struck a deal with the largest natural food chain in America, Whole Foods, which started selling packs of fonio this year.
"The first location (Harlem) is selling really well and we are now planning to unroll through their 36 Northeast region locations," he said.
He is keen to continue pushing fonio even further, and his dream is to see his native grain developed into every food type on the market.
"We have developed several fonio products that we plan to gradually introduce to the market. Crackers, cereals and pastas."
If Thiam's dream comes true, fonio could rival quinoa around the world.