Best ways to preserve black truffles, long term

Keeping for several months, a few options:

Freezing the truffles
Wash and brush the truffles as described above, allow to dry, wrap in aluminium foil or in vacuumed plastic bag and store in freezer. When it is cooking time, thinly slice the frozen truffles. This way they will retain their natural juice and their full aroma.

Preserving in alcohol
Wash and brush the truffles as described above, allow to dry, place in a jar and cover completely with cognac. However, keep in mind that cognac might overwhelm the truffles’ natural flavor.

Preserving by sterilization
Place the washed and brushed truflles in a small jar. Add a little salt and a teaspoon of water for every 50 grams of truffle. Seal the jar airtight. Sterilize at boiling temperature (100°C or 212ºF) as follows:
2 hours for less than 40 grams (1.5 oz)
3 hours from 40 to 100 grams (1.5 to 4 oz)