Abstract: A closure for covering the opening of a vessel containing a supply of cooking fluid preferably includes a flexible inner member adapted to cover the opening of the vessel in sealing engagement therewith and an outer member adapted to be positioned above the inner member. A coupling assembly is provided to couple the inner member to the outer member when the closure assembly is removed from the vessel. The coupling assembly permits a portion of the inner member to expand away from the outer member in response to an increase in temperature within the cooking vessel. The inner member is preferably a low thermal conductivity material so that after the inner surface of the inner member, which is exposed to vaporized cooking fluid, reaches the temperature of the vapor condensing thereon, the rate of additional condensation is substantially reduced. The vapor conserved by reduced condensation on the inner surface is used to generate pressure in the vessel more rapidly.