A cooker, comprising: a planar structural layer ; and a cooking surface layer extending over the planar structural layer to provide a cooking surface ; characterised by : a liquid layer contained between the planar structural layer and the cooking surface layer ; an elongate cooling channel , arranged such that in use liquid in the liquid layer flows into the cooling channel and out of the cooling channel into the liquid layer , the cooling channel being formed of a thermally conducting material ; and a first actuator controllable to raise and to lower a first region of the cooking surface layer and a second actuator controllable to raise and to lower a second region of the cooking surface layer thereby to generate a flow of liquid in the liquid layer , the first and second actuators being controllable alternately to raise and to lower the respective regions of the cooking surface layer in a predetermined sequence, thereby to induce a flow of liquid within the liquid layer , including a flow of liquid from the liquid layer into the cooling channel and a flow of liquid out of the cooling channel into the liquid layer . a planar structural layer ; and a cooking surface layer extending over the planar structural layer to provide a cooking surface ; characterised by : a liquid layer contained between the planar structural layer and the cooking surface layer ; an elongate cooling channel , arranged such that in use liquid in the liquid layer flows into the cooling channel and out of the cooling channel into the liquid layer , the cooling channel being formed of a thermally conducting material ; and a first actuator controllable to raise and to lower a first region of the cooking surface layer and a second actuator controllable to raise and to lower a second region of the cooking surface layer thereby to generate a flow of liquid in the liquid layer , the first and second actuators being controllable alternately to raise and to lower the respective regions of the cooking surface layer in a predetermined sequence, thereby to induce a flow of liquid within the liquid layer , including a flow of liquid from the liquid layer into the cooling channel and a flow of liquid out of the cooling channel into the liquid layer . a liquid layer contained between the planar structural layer and the cooking surface layer ; an elongate cooling channel , arranged such that in use liquid in the liquid layer flows into the cooling channel and out of the cooling channel into the liquid layer , the cooling channel being formed of a thermally conducting material ; and a first actuator controllable to raise and to lower a first region of the cooking surface layer and a second actuator controllable to raise and to lower a second region of the cooking surface layer thereby to generate a flow of liquid in the liquid layer , the first and second actuators being controllable alternately to raise and to lower the respective regions of the cooking surface layer in a predetermined sequence, thereby to induce a flow of liquid within the liquid layer , including a flow of liquid from the liquid layer into the cooling channel and a flow of liquid out of the cooling channel into the liquid layer . <EOS>