¹⁸O'Kelly, Michael. "Excavations and Experiments in Ancient Irish Cooking-Places." The Journal of the Royal Society of Antiquaries of Ireland 84.2 (1954): 121-22.
One example from the "early Irish literature" might be from Keating's Foras Feasa ar Éirinn (1723, from Medieval sources): "However, from Bealltaine until Samhain. the Fian were obliged to depend solely on the products of their hunting and of the chase as maintenance and wages from the kings of Ireland; thus, they were to have the flesh for food, and the skins of the wild animals as pay. But they only took one meal in the day-and-night, and that was in the afternoon. And it was their custom to send their attendants about noon with whatever they had killed in the morning's hunt to an appointed hill, having wood and moorland in the neighbourhood, and to kindle raging fires thereon, and put into them a large number of emery stones; and to dig two pits in the yellow clay of the moorland, and put some of the meat on spits to roast before the fire; and to bind another portion of it with suagans in dry bundles and set it to boil in the larger of the two pits and keep plying them with the stones that were in the fire, making them seethe often until they were cooked. And these fires were so large that their sites are to-day in Ireland burnt to blackness, and these are now called Fulacht Fian by the peasantry."
Poet Nuala Ní Dhomhnaill evokes the image of the Fenian warriors at their Fulacht Fian in this excerpt from her poem "The Lay of Loughadoon:"

"We walked on till we found
a megalithic tomb or burial-mound,
wedge-shaped, with a great capstone, and by it
an ancient cooking-pit.

'While they hunted,' I went on to say,
'Fionn and the Fianna
ate only one meal a day
and that usually in the evening.

Their stewards used to light great fires
and dig two pits, in one of which
Fionn and the Fianna would wash
while their dinner cooked in the other.'"

(Ní Dhomhnaill, Nuala, and Paul Muldoon. The Astrakhan Cloak. Winston-Salem, NC: Wake Forest UP, 1993. 67.)