Whole fresh mushrooms don’t really freeze well with the exception of truffles – their structure is too delicate and soft to survive harsh temperatures – but here’s a tip to get around this.
Freeze the mushrooms in stock
Fry some finely chopped onion in a little olive oil until the onions are soft, add finely sliced mushrooms and fry over a high heat to release their liquid. Add white wine or stock and cook over gentle heat until the mushrooms are cooked. Leave to cool and freeze this mixture in an ice cube tray, adding water to top up the ice cubes if needed. When the ice cubes are frozen, transfer the ‘cubes’ to ziplock bags and store in the freezer. Add the frozen cubes to stews, risottos and pilafs.
Truffles can be frozen if you find yourself with a surfeit (though we find it hard not to eat a truffle when we buy one). To freeze truffles, wrap each individual truffle tightly in a few layers of tin foil, place in a freezer container, cover with a lid and freeze. You don’t need to thaw them before using them in cooking – just slice or grate the frozen truffle straight into the dish. In fact, defrosting truffles will cause them to become soft and pulpy. Never defrost and refreeze a truffle. However, if you take the truffle out of the freezer briefly to shave some into a dish, and it hasn’t defrosted, you can wrap it again in tin foil and pop it back into the container for use next time.