A method of extracting an essential oil from plant matter, starting with providing plant matter to an interior of an extraction vessel, wherein the plant matter includes at least one essential oil. Next, at least one vacuum pump is used to reduce the pressure within the interior of the extraction vessel with the plant matter therein to an absolute pressure of less than 1.0 mm Hg absolute pressure. Microwave energy is applied to the plant matter while the interior of the extraction vessel is under the reduced pressure, thereby forming a vapor including at least a portion of the essential oil. The vapor is directed from the extraction vessel to at least one condenser vessel. Finally, the vapor is condensed to a liquid state such that the vapor includes at least a portion of the essential oil, by utilizing the at least one condenser vessel.