Start by thoroughly washing your mushrooms. Then slice your mushrooms. After you have them all cut up you will want to blanch them. This will make sure that they aren't mushy when you go to cook with them. Fill a pot halfway with water and bring it to a boil. Then, add your mushrooms.

Let them boil for about 1-2 minutes depending on the size of the mushrooms. Then quickly move them to a bowl with ice water. This stops the cooking process so the mushrooms don't overcook.

Once the mushrooms have cooled you can place them on a cookie sheet. You can either use wax paper or a silpat mat. Place them in the freezer for about 30-60 minutes. Once they are frozen you can then place them in a freezer safe container. They will last 6-8 months in the freezer.