Inspired by the best meal we had in Paris, at Un Jour a Peyrassol. Goes with the potato gnocchi.

2 tb Butter
2 c Stock, chicken (or vegetable)
4-6 Mushrooms, finely chopped
1 c Cream, heavy
2 tb finely chopped shallots
1 c Wine, dry white
1 ts Peppercorns, crushed
4 tb Truffles, finely chopped OR 1 teaspoon truffle oil (to taste)
2 Bay leaves
Salt (to taste, do not use if using concentrated/bouillon stock)
Pepper (to taste)

Melt the butter in a saute pan. Add the mushrooms, shallots, peppercorns, and bay leaves. Reduce the mixture over high heat for about 2 minutes.

Add chicken stock and continue cooking over medium heat. If using truffle oil, also add the white wine at this point. Reduce by 2/3rds

Add cream, bring the mixture to a boil, then reduce by one-third and make it a smooth consistency. Adjust the seasoning.

If using fresh truffle oil, In another saute pan, add 1/2 cup wine to 3 tablespoons of truffles. Reduce over high heat for 2 to 3 minutes. Strain (optional) the cream sauce into the truffles and wine, then reduce it to a smooth consistency. If using truffle oil, skip

Remove from heat, whisk in truffle oil.

Source: Great Chefs (Masataka Kobayashi, Masa's, Vintage Court Hotel) of San Francisco, Avon Books, 1984 via http://www.recipesource.com/side-dishes/sauces/12/rec1227.html ; Truffle oil adjustments via http://www.epicurious.com/recipes/food/views/Black-Truffle-Sauce...