I got this recipe from Linda Terpstra who got it from a cookbook. I think she said it might have been one of those Dallas classics like the Arboretum or such. But it's such a basic I figure it's in every cookbook in America. I loved the mushroom soup at Monk's Oven restaurant and when they closed the restaurant, I told Shannon Monk I wanted her to give me the recipe. But she said it was in another cookbook and I could find it there. So apparently, it's not any big secret.
Linda and I use 4 tablespoons of flour. I also only use 1 cup of whipping cream so that it's slightly thicker. I also throw in a dash of sherry.
It freezes well so when I make it, I always freeze the leftovers in 1-pint Ziplock bags. It's great for an impromptu fancy lunch.