Note: There is another version of the mushroom sauce in classical cuisine, but it is a demi-glace-based sauce that can be served with meat and pork dishes. See the recipe for Mushroom Sauce I.
- In a heavy-bottomed saucepan, heat the butter over medium heat until it's frothy. Stir in the lemon juice, then add the mushrooms and sauté until soft, about 5 minutes.
- Stir in the Allemande or Suprême Sauce. Bring to a simmer, cook for another 5 minutes and serve right away.