- Nansen Cooker
A very efficient cooker which used 90% of the fuel for cooking when in operation, devised in the 19th century by the Norwegian Arctic explorer Fridtjof Nansen.
"The hot gases from the combustion of the kerosene, before they escape into the outside air, have to circulate along a tortuous path, passing from the hot interior to the colder exterior compartments, losing heat all the time. Thus a hot hoosh is preparing in the central vessel side by side with the melting of snow for cocoa or tea in the annulus. By the combination of 'Nansen Cooker' and primus stove one gallon of kerosene oil properly husbanded is made to last for twelve days in the preparation of the ordinary ration for three men."
A Nansen cooker is highly efficient but also highly specialized. I think you need to be Norwegian or you aren't allowed to even touch one.