Homemade Cream of Mushroom Soup

I think canned cream of mushroom soup is an ingredient in almost every single American casserole, isn't it? I finally started making it from scratch. It takes a bit more effort, so casseroles aren't as easy to throw together, but the taste is out of this world delicious. Make sure you use organic cream, preferably not pasteurized. I hope to make it out to Urban Acres soon where my friend, Nicole, told me I can get low-pasteurized cream. I'm wondering if this sauce would freeze. Well, haha... ice cream obviously freezes... thoughts on if this mushroom sauce would freeze?
-Amanda

Mushroom Sauce:
a lot of mushrooms- 5 cups or so
1/2 large onion finely diced
1 pint of heavy cream preferably not pasteurized, but I haven't been able to get any of that yet.
1/4 cup flour - I used whole wheat
3 tbsp butter

To make the mushroom sauce, chop onion very small and place it in a large skillet with melted butter. Chop mushrooms as small as you like. Since I was again, mimicking the canned sauce, I chopped them fine since the canned stuff almost doesn't even hint at mushroom.... strange, right? Add the mushrooms to the softened, translucent onions and cook until they have cooked down quite a bit. Add more butter if the skillet is dry. Sprinkle flour across mushrooms and stir until there is no dry flour left. Pour in cream and bring to a boil to thicken.