You can freeze au jus by first allowing it to cool, then adding it to an airtight freezer-safe container with at least half an inch of space at the top. A freezer-safe bag also works for freezing au jus. If you would like easier portions, freeze in an ice cube tray first, then move to a freezer-safe bag. Store in the freezer for up to 6 months and reheat on the stove over low heat.