I made Balthazar's mushroom soup (recipe on 101 cookbooks). It's a fully puréed soup with approx 2 lb mushrooms, 6 cups broth, and 1 cup cream. Even if it initially separates, can't I give it a whir in the blender?
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This probably won't help but I usually find it helpful to freeze soups minus the cream and then add it after I've defrosted and heated up. I love Mrs Wheelbarrow's mushroom soup and in the unlikely event I make too much I freeze the mushroom/stock base and then add the cream once I defrost and cook.
I think you could totally try it in the blender. Good luck!
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It may be perfectly okay...it may separate. The blender idea is a good one. You can also heat up some cream and add it while whisking. That may bring it back together.