Cream of mushroom
finely chop some raw mushrooms and 1/2 as much onion.
Melt 4 T butter in a large heavy-bottomed skillet, and when the butter starts to bubble, add veggies. Stir continuoulsly over medium-low heat, add a pinch of thyme and salt. When onions turn translucent, add 3 T flour, and continue to stir till flour turns golden.
Add 2 -3 cups cold milk gradually from a pitcher or measuring cup, stirring in a circular motion all the while with a whisk (a flat whisk is best for this job, but a regular whisk or large fork will do).
Cook slowly, stirring often to prevent any milk from sticking to the bottom as it thickens. Should take about 10 minutes to do so. Season with s & p to taste. I like to add just a tiny grating of nutmeg at the last, for flavor and fragrance.
This sauce can be thinned a bit for soup, or used as a base for any casserole that needs a sauce to bind ingredients during baking. Add some flavorful cheeses, for instance, and you have Mac N Cheese. Add veggies and chicken and you have Chiken Divan. Create your own combos. Possibilities are endless.
Are we talking soup here?
Saute 1 1/2 cups sliced/chopped mushrooms in 2 Tbsp. butter until just slightly browned. Set aside.
Heat 2 cups chicken stock.
Saute 1 finely chopped shallot in 1 Tbsp. butter until slightly soft.
Add mushrooms to the onions to heat through.
Meanwhile, prepare a roux with 1/4 cup flour and 1 Tbsp. butter. When roux reaches color you're looking for, combine it with the chicken stock and whisk over medium heat until smooth. Simmer for 5 minutes, stirring frequently.
Add onion/mushroom mixture and choice of seasonings (S&P, herbs and or spices of choice).
Meanwhile, warm 1 cup cream over low heat and, when stock mixture is at simmer, remove stock from heat and stir in the cream.
Taste and adjust seasonings.
Allow to remain at low heat, but DO NOT boil, 15 - 20 minutes.
re: Dark Wanderer
Not quite the same but, if it's all you have, you could use it. Mushrooms are naturally hygroscopic so if they're already saturated with the liquids in the can they're not going to absorb as much of the butter flavor as they otherwise might. Just drain them and pat them dry before dropping them into the butter. You may also have to turn the heat up a bit more than you ordinarily would for that step. Be careful not to burn the butter.
Basically, this is just making a mushroom puree and mixing it with a bechamel; it's really good.
Half a pound of mushrooms, one onion (peeled, sliced), half cup red wine, 2 cups chicken broth. Take the tops off the cutest mushrooms, slice prettily, and set aside; chop the rest. Put chopped mushrooms and onion in a 6-quart or so pot with liquids, bring to a boil, reduce heat and simmer (partly covered) 25 minutes.
During that time (or before, or whenever), you can scald 2 cups milk in a small pan, then in a larger pan make a light roux whisking together 2 Tablespoons flour and 3 Tablespoons butter and gradually stir in the scalded milk. Cook on low for about 10 minutes, whisking occasionally. Add salt and pepper to taste.
Puree the mushroom/onion/liquid (preferably in the pot with an immersion blender). Combine the white sauce with the mushroom puree (stir it in slowly and carefully), then add reserved mushrooms and let them poach as you bring it to a boil, then turn off heat.
Everyone seems to like this.