Cook mushrooms: Add mushrooms and cook for 10–12 minutes, stirring occasionally, until browned and most liquid evaporates. Season with salt and pepper.
Add flour: Sprinkle in flour and stir well to coat the mushrooms. Cook for 1–2 minutes to remove raw flour taste.
Pour in broth: Gradually add broth, stirring to prevent lumps. Bring to a gentle boil, then reduce to simmer for 10–15 minutes, stirring occasionally.
Blend (optional): For a smooth soup, use an immersion blender or transfer half (or all) to a blender. For a chunky texture, leave as is.
Finish with cream: Stir in the heavy cream. Simmer for another 5 minutes. Adjust seasoning with salt and pepper.