Matsutake mushrooms are a Japanese mushroom grown in the red pine forests and harvested each autumn. The Japanese mushrooms are extremely expensive so even the Japanese people purchase less expensive imported varieties. Available fresh or dried matsutake mushrooms have a firm white flesh with a distinctive aroma of cinnamon and pine and a firm, chewy texture.
You most likely won't find these in your neighborhood grocery store (in most places in the U.S.) but you can find them online at Oregon Mushrooms. Also look for them in your local farmer's market.
If you don't have matsutake mushrooms you can substitute: