Best use for mixed mushrooms?

Sautee with garlic, sage and parsley by all means. In order to showcase the mushrooms you could serve them over a soft polenta.

Mushroom lasagna. Ina has a good recipe.

Also from Smitten Kitchen (originally from Gourmet) - I've done this recipe a few times: http://smittenkitchen.com/blog/2010/12/garlic-butter-roasted-mushrooms/
Really good, served just like she shows with some crusty bread to soak of the juices. You can use any kind of mushrooms. Maybe a good first course or appetizer, depending on how much you have.

The Smitten Kitchen link for Mushroom & Stilton Galette is:
http://smittenkitchen.com/blog/2006/10/when-the-funk-hits-the-fan/

You lucky devil. Enjoy them!

Fricassee of Chanterelles
http://www.bonappetit.com/recipe/fricassee-of-chanterelles

Mushroom & Stilton Galette
smittenkitchen.com

Wild Mushroom Bread Puddings (individual)
http://www.epicurious.com/recipes/food/views/Wild-Mushroom-Bread-Pudding-240982#ixzz2j31jY6cE

Mushroom Stroganoff
http://food52.com/recipes/11201-mushroom-stroganoff

Here is the wild-rice mushroom soup link http://www.williams-sonoma.com/recipe/wild-rice-and-wild-mushroom-soup.html?cm_src=RECIPESEARCH

I have been on a mushroom kick lately and tried this dish last week. It was great and the mushroom flavor was very prominent. http://food52.com/recipes/5710-farro-salad-with-roasted-mushrooms-and-parmesan

Sunset Magazine had a beautiful salad last month with mushrooms roasted in a 400º oven (drizzle olive oil, seasoned with salt and pepper and fresh thyme leaves) roast 15 minutes. Served with a dressing of shallot, sherry vinegar, hazelnut or olive oil. Served over mixed lettuces and garnished with shavings of manchego sheese and roasted hazelnuts. It was delicious; you could also use roasted mushrooms on their own, adorning a soup (williams-sonoma has a terrific mushroom soup on their site. I make a variant of it for T-giving every year). Roasting the mushrooms concentrates their marvellous flavor.

I like to sauté in butter and then add Italian or Caesar bottled dressing for marinated mushrooms. I always use sliced button mushrooms since I don't usually have the mixed. It might overpower the mixed mushroom flavors.

You could saute them and then add to a light cream sauce, which I would make with a combination of chicken(or turkey) broth and cream.