An apparatus 10 is provided for heating and processing a product. A mixing bowl 12 includes a rounded base portion, an extended upper portion and two end walls. An agitator is positioned within the base of the bowl 12 for rotation about a rotational axis and in a closely spaced relation with the bowl 12. The agitator includes a drive shaft having a portion thereof projecting outwardly of the mixing bowl 12. The agitator having a rotational path closely spaced with the inside wall of the base portion and spaced from the upper portion of the bowl 12. An outwardly flared transition 54 maybe provided between the base and upper portion of the bowl. A microwave energy source 30 is directed into the bowl for heating the product. A choke 78 surrounds the agitator shaft to form a seal for the bowl 12 to prevent microwave leakage.