"This is witchcraft," says a woman as she opens a Wonderbox and finds a pot of cooked lentils and rice inside, steaming hot.
"No, it is science," says the presenter. "Aaaah!"
The presenter is trained by Vuka Energy Savings, and she is showing people in the Stanford community how to save time and energy — both their own energy as well as paraffin and electricity.
Villagers formed the Stanford Housing & Development Co-operative in the Western Cape in 2007 to lobby for low-cost housing.
While waiting for action from the government, the idea arose that home owners would need to know how to use the electricity they hoped would be installed in the first home they'd ever owned.
Elma Hunter, the co-operative's secretary, had previously used old-fashioned hayboxes to cook food and she started Vuka Energy Savings.
The project has given six trained presenters Wonderboxes, three have been given brick rocket stoves and one a drum rocket stove. All these simple cookers use insulation to save energy.
Driven by their own experience of using the simple technology to save money, the presenters go into the community and demonstrate them at homes, libraries and clinics.
At the same time they show each household that it has all that's needed — such as a blanket, duvet, towels or newspaper — to make their own heat-retention wonderbox.
They also demonstrate other energy-saving technologies such as solar cookers and lights.
"We are saving at least R300 a month in my home," says one of the trainers. "There are four shacks in my yard and they now know how to use the brick or drum rocket stove to heat water.
"Using small twigs, they cook food for 10 to 30 minutes and put the pot into the Wonderbox which I provide. When Stanford could not access pre-paid electricity for 27 hours recently, we had cooked food and hot water."
Vuka has trained four Afrikaans and 13 isiXhosa presenters; nine work in Hermanus and the rest work in Stanford.
The team makes decisions about their future plans and how best to teach community members. Hunter raises donations to pay for the groceries needed for demonstrations, though often this money comes out of her purse.
Stanford residents are now making and selling Wonderboxes and profits are ploughed back into the project.
Residents have become creative with these low-tech solutions. A Stanford marketer now makes yoghurt in glass jars wrapped in mohair blankets, while a subsistence farmer who had lost a brood hen to a predator, managed to use the Wonderbox concept to complete the incubation of her eggs.
Benefits extend beyond the reduced use of wood, electricity, gas or paraffin, says Hunter.
The ever-present danger of fire in homesteads is also reduced, as is damage to trees and the harm to people's health caused by wood and paraffin stoves used in a confined space. It also saves women time which can be better spent on other tasks.
The concept should be replicated all over South Africa, says Hunter. "It would have a great impact on the environment if every household and people of all incomes were conscious of and used these simple technologies."