Preserve Fresh Herbs in Olive Oil (the Safe Way)
A glut of summer herbs and a bottle of olive oil add up to free flavour all winter — if you do it safely. Here is the method, and the one safety rule that matters.
Herbs go limp and brown in the fridge within days. Olive oil locks their flavour in — but the right way is to freeze, not to leave jars of herb-in-oil sitting on the counter.
The ice-tray method
Chop basil, parsley, rosemary, thyme, sage — whatever is going over — pack into an ice-cube tray, cover with olive oil, and freeze. Pop out the cubes, bag them, and drop one straight into a hot pan whenever you cook. Instant herb-and-oil, months later.
Do not store fresh garlic or herbs submerged in oil at room temperature. Oil seals out air, and that low-oxygen, low-acid environment is exactly where the bacterium behind botulism can grow — it has caused real poisonings. Keep herb-and-oil mixtures frozen, or refrigerated and used within a few days. Frozen cubes are completely safe and just as useful. When in doubt, freeze it.
Use a plain, decent oil for this — save your peppery extra virgin for finishing — and you will be pulling summer out of the freezer in January.