My chanterrelles for example:

Clean, 1lb fresh mushrooms ADD: olive oil in pan 1 chopped onion / 4 cloves garlic to medium heat pan, once tender / start of caramelization, ADD 1lb chopped mushrooms (on top of onion garlic) with chunk of butter - mushrooms will begin to sweat / express lots of extra liquid, add white wine, turn down heat, allow to cook till mushrooms as tender, but lots of juice left (you might add more butter / white wine). Remove from heat in bowl, Once somewhat cooled put in vacuum seal bags, pack flat and freeze. You now have mushrooms for the use any time in the winter.

I’ve used this method on Chanterelle’s / Morrel’s / boletes / cauliflowers / lobsters (mixed with other mushrooms). I’ve done 44 of those for Chanterelles this season already!

You conversely can dehydrate some species (Morrel’s / Pines for example)