The design consists of the visual features of the portions of the cooking unit shown in solid lines in the drawings. Throughout the Figures, where shown: (i) the dotted lines showing additional structure of the cooking unit are for illustrative purposes only and form no part of the claimed design; (ii) the unshaded surfaces do not form part of the claimed design; and (iii) the dotted/dashed lines illustrate unclaimed boundaries of surfaces claimed as part of the design. Portions of the cooking unit not shown in the Figures and not otherwise described in this Specification do not form part of the claimed design.