Bordelaise Sauce - Great Grilled Red Meat Sauce

I found this recipe in a Viking Cruise brochure for Longboat river trips in France.  I have been making a version of this sauce for family and friends for some time.  Upon review, I think this one will be far better than mine.

The author of this recipe is Georges Auguste Escoffier.  It appeared in this book "Le Guide Culinaire" first published in France in 1903.  George Auguste Escoffier was a French chef, restaurateur and culinary writer who popularized and updated traditional French cooking methods.  Among his achievements, he codified the recipes for the five mother sauces.   So, enjoy.

Ingredients

• 2-½ cups Beef demi-glace. It is expensive, but worth every penny. 
• You can purchase demi-glace from William Sonoma, and I would assume other specialty food stores.  The only place I have found it is at William-Sonoma.  William-Sonoma sells beef, chicken and veal demi-glace.  
• 1-¼ cups Bordeaux wine.
• 1 finely chopped Shallot
• Ground pepper to taste
• 1 whole Bay Leaf
• 1 sprig of fresh Thyme or ¼ teas. dry Thyme
• Sauted mushrooms, if your desire.  (I would add only about 1 cup - reduced volume).  Saute fresh mushrooms, patted dry, in butter until browned).
• 1 teas. butter
• 2 oz. Bone marrow, poached and diced (you can secure bone marrow from most high end meat market counters).  This will give the sauce more depth, but can be left out if you wish. 

Procedure

• Warm demi-glace in medium sized saute pan over medium heat until desolved.
• In another pot, bring the wine, shallot, pepper, Bay Leaf, and Thyme to a gentle boil.  Cook slowly until reduced to ¼ cup in volume. 
• Add demi-glace and simmer on low-medium heat for 15 minutes.
• Strain the sauce.
• If you sauted mushrooms, add them to the strained sauce.
• Finish with butter and bone marrow.