Galen
I adore French cooking. Have you a good recipe for a sauce Robert as it's one of my favourites.
Sauce Robert belongs to an old repertoire of French cuisine and if i did do this sauce, I wouldn't use demi-glace as it's to heavy and rich. I would use brown chicken stock, but for a quick recipe, 10g of butter, 100g of onion (chopped finely), 70g of white wine (dry) and 100g of brown chicken stock, 15g mustard.
Sweat the onion in butter for 5 minutes, add the wine and boil to remove alcohol, whisk in the mustard, add the chicken stock, reduce until it coats the back of the spoon.
p.s a little bit of fresh herbs such as tarragon, thyme or rosemary will add character to your sauce.