From The Fanny Farmer Cookbook
Unless mushrooms are very dirty, trim off the hard end of the stems and just wipe them clean with a damp cloth or paper towel.
5 tablespoons butter 1/2 pound mushrooms, sliced 2 tablespoons flour Juice of 1/2 lemon 1 cup heavy cream Salt to taste
Melt the butter in a large skillet. Stir in the mushrooms and cook for 2-3 minutes, until they darken a little. Stir in the flour, blend to smooth, and cook 2 minutes. Slowly stir in the lemon juice, cream, and salt, and cook only until hot.
Makes 1-1/2 cups