Truffle oil is definitely a gourmet ingredient. It lends an aroma and umami quality that is totally unique. Many truffle oils available at supermarkets aren't actually made from truffles, but from chemical compounds that mimic the mushroom-like organism's distinctive qualities. Making it yourself is a good way to make sure your truffle oil is authentic. It is an initial investment, but totally worth it if you can afford the truffles, which are expensive.
White truffles are the rarest and most desirable. Black truffles are great, too, but have a slightly different flavor. Acquire very ripe truffles, which emit the strongest aromas. (Unripe truffles have no flavor.) Use the ripe truffles immediately, as they'll lose their potency quickly.
Warm 1 to 2 cups high-quality extra-virgin olive oil in a pot over low heat. Bring up to a warm temperature, but not simmering or boiling.
Shave or finely dice pieces of the ripe truffle into the warm oil.
Transfer oil and truffles to a jar or bottle, cover with a lid or cork, and let the mixture steep for several hours or days in a cool, dark place. The longer it steeps, the stronger the flavor.
You can store homemade truffle oil in the refrigerator for up to 2 weeks. It may solidify and turn opaque, but the flavor should stay intact.
For optimal flavor, remove as much oxygen from the container as possible using a nitrogen gas dispenser made for wine enthusiasts. Other methods of minimizing oxygen exposure include plugging a bottle with a cork and sealing wax, or covering the surface of the oil with plastic wrap.
Once your oil is infused, remove the bits of truffle and use them in other dishes like scrambled eggs or a cream sauce.
Truffle oil is a finishing oil—added just before serving to enhance flavor—and should never be used for cooking. Just a drizzle of the oil over risotto, salad, popcorn, soups or bread is enough to infuse the dish with the distinctive flavor.
If you choose to store truffle oil in the refrigerator, keep in mind that repetitively moving the oil from cold storage to room temperature could negatively affect its delicate flavors.