"That's when you find out how good your weaving is," said co-organiser Rewi Spraggon as he demonstrated the technique.
"If there's holes in it, there'll be dirt in your food." I tucked my weaving, which looked like a bird's nest that had been through the heavy wash cycle, quietly out of sight.
"A lot of Kiwis, Maori and Pakeha, grew up knowing hangi and doing it," Spraggon told me. "But we are losing it, I think."
He fears that hangi belongs to the era of the quarter-acre section when communities were more homogeneous and families' social connections, often mirroring the menfolk's working-life ones, were much stronger.
"We don't have that now. It's fading away, which I think is sad."
The kitchen prep team cut kumara and potato under the eye of Eynon Delamere, a man given to colourful exaggeration ("my mum told me the secret to a good stuffing: 10 pounds of butter"), always followed by a self-deprecatory, "nah".
He was doing a poor job of concealing his disdain for pumpkin ("it cooks too fast and turns to mush") and extolling the virtues of peppery kawakawa leaves, scattered over the pork, beef, chicken and lamb, all of which had been halal slaughtered.
Delamere reminded me that the key to a good hangi (apart, that is, from butter) is the choice of stones: sedimentary river rock can explode and the best rock is, unsurprisingly, volcanic.
"Once you get them, you hold on to them for a lifetime," he said. "I bury mine, so if someone wants to borrow them they have to dig them up. They don't usually want to do that."
Back at the pit, the ash had been dug out from around the rocks and after a few cracks about how this was actually a firewalking workshop, the wire baskets were lowered into place. There was a brief moment of panic when someone noticed that none of that butter had made it into the hole in the cored cabbage, and then the woven mats went on. A light dousing of water ensured heat became steam and the earth was mounded up. Those standing nearby were deputised to watch for and tamp down steam leaks.
The public interest in the free workshops (there's another this weekend but both were fully subscribed long ago) was notably strong among immigrants, something that Riki Bennett noticed when workshops were offered a few years ago.
"A lot of immigrant communities want to have the opportunity to engage with Maori culture but don't quite know where to make the connection," he said.
Jason Zhou, who had come along with his wife Jing Li and their daughter Trinity Chow, said he had been raised in his native China to respect his culture and history.
"When I heard about this, I thought 'bang on', because it's old-school stuff. It's good to learn about the long history and the significance of things."
Jagroop Singh, a Sikh chef (whose goat curry was a hit at the lunch shared while the hangi was cooking) was fascinated to learn about the cooking technique which his partner, Tania Allen, of Ngapuhi ancestry, had told him about.
"Usually, when we are putting down hangi, it's for tangi or weddings and everyone's under pressure," Allen said. "But today is about learning and it's good to relax."
