Proceed with pasteurization: After they have been sterilized, fill the jars leaving about 0.5 cm of headspace. If using the hot-water bath method of sterilization, preheat the jar under hot running water to prevent the glass from breaking due to thermal shock and then dry the jar. To avoid burns always handle the hot jars with oven mitts or potholders. Should air bubbles form, remove them by lightly pushing down on the preparation with a spoon. Clean the edges of the jars and tighten the lids without using excess force (closing too tightly does not allow air to escape and therefore a vacuum does not occur). Place them in a heavy-bottomed pan with the lids facing upward. To prevent the jars from bumping each other and breaking during boiling, put a clean dishcloth between the jars. Cover completely with warm water and bring to a boil. Once a boil is reached, boil for another 30 minutes. The Quattro Stagioni jars must always be covered with water. Once the jars have cooled, check that the centre of the lid has depressed (a sign of correct pasteurization) and store in a cool place.