Place mushrooms in a large stockpot; cover with water. Bring to a boil; stir. Reduce heat; cover and simmer for 3 minutes or until tender. Drain well.
In a Dutch oven, melt butter. Stir in flour until smooth; gradually add milk and evaporated milk. Bring to a boil; cook and stir until thickened, about 2 minutes. Stir in salt and mushrooms. Cook and stir over medium heat until heated through, 3-4 minutes.