Heat a medium sauce pan over medium heat, add 2 tablespoons of butter and when hot, add the mushrooms.

Saute the mushrooms until they release their liquids and begin to lightly brown.

Add the minced shallot and cook for a minute or two until they start to soften.

Add the tomato sauce or dice tomatoes along with the wine and Cognac and bring to a boil.

Immediately reduce the heat to a simmer and continue cooking until most of the liquids have evaporated. This could take as much as 10 minutes.

Add the demi glace and fresh parsley and continue to reduce the sauce for 5 minutes or until it is thick enough to coat the back of a spoon.

Season with salt and pepper, to taste.

Add the remaining tablespoon of butter (mounting) to give the sauce an extra shine and richness.

Taste and adjust seasonings with S&P.