Directions
Heat 1 tablespoon of butter with the olive oil in a large skillet over medium heat. Add the onion, mushrooms, salt, pepper and thyme. Cook until the mushrooms have browned slightly and the onions are soft and tender, about five minutes
Add the chicken broth to the mushroom mixture. Bring to a boil, then reduce to simmer. Simmer for five minutes. Remove the pan from the heat to cool.
Once the mushroom mixture has cooled a bit, remove about a half cup of the mushrooms and onions to set aside. Pour the rest of the mushroom mixture into a blender and puree. Set aside.
In a saucepan, melt the 3 tablespoons of butter over medium heat and then add the flour, stirring to blend well. Cook the flour mixture a minute or two and then add the half and half, stirring to combine well. Add the mushroom puree and the reserved, chopped mushrooms and onions. Heat until hot and thickened. Remove from the heat and add the sherry and nutmeg. Taste for seasoning and add additional salt and pepper as needed. Serve.