A cooking apparatus having a polygonal skillet comprising a bottom plate with depending walls and an exteriorly mounted sealed jacket spaced away in communication with a heat source for heating a condensate contained within the jacket to a vapor that will circulate around the substantially planar surfaces of the skillet confined by the jacket with the jacket positioned to form a condensate return slope. The jacket and skillet have a plurality of anchoring fasteners extending therebetween providing a cooking apparatus having an enclosure capable of 400 psi, which is not in the prior art that consist substantially of radial cross section vessels of lesser pressure capability.