1. Melt the butter in a large saucepan or Dutch oven and sauté the onion, garlic, scallions and ham for 5 minutes.
2. Add the mushrooms, reduce the heat to medium and cook for for 2 minutes.
3. Blend in the flour and cook, stirring for 4 minutes, then add the Worcestershire sauce, beef stock, wine, thyme and bay leaf. Simmer very slowly until the sauce thickens, about 1 hour.
4. Before serving, remove the bay leaf and add the parsley.
5. Season with salt and pepper to taste.