Based on the provided search results, “Sauce Bercy” is a classic French white sauce traditionally used to accompany fish, seafood, or sometimes steak. 
It is not a widely marketed, pre-packaged retail brand name but rather a culinary sauce definition. Here are the key details: 
Main Ingredients: The sauce is made from a base of white wine, shallots, butter, fish stock (or fish velouté), and parsley.
Flavor Profile: It is described as a velvety, buttery sauce with a delicate flavor.
Usage: It is designed to be served with fish, seafood, or pan-fried chicken breast.
Origin: The sauce originates from the Bercy neighborhood of Paris. 
Context regarding “100g”:
While there is no specific product named “Premium Sauce Bercy 100g” in the search results, traditional recipes, such as those in Le Guide Culinaire by Auguste Escoffier, often involve using roughly 100g of butter to finish the sauce for a recipe serving.
Some high-end or gourmet suppliers (like Spanish-oil, which highlights it in their spices) consider it an essential French culinary component. 
In summary, it is a high-quality, butter-based white wine reduction sauce commonly prepared fresh for fine dining, rather than a mass-marketed 100g packaged product.