Premium Mignonette Sauce 250 g” is a commercial quantity (250 gram container) of mignonette sauce, a classic, piquant condiment traditionally served with fresh, raw oysters. 

Description
The sauce is primarily vinegar-based and is characterized by its light, sharp flavor that is intended to complement, not overpower, the natural, briny taste of oysters. The “premium” designation suggests a high-quality product, likely using superior ingredients like champagne or a specific wine vinegar. 

Key Ingredients
The core ingredients of a classic mignonette sauce include: 
Vinegar: Typically red wine vinegar or white wine vinegar, though variations may use champagne, sherry, or even fruit-infused vinegars.
Shallots: Finely minced eschalots (French shallots) provide a mild, sweet allium note and texture.
Cracked black pepper: The French term “mignonette” originally referred to a sachet of spices, but now commonly means cracked pepper, which adds a subtle bite. 

Usage
It is usually served chilled, alongside freshly shucked oysters on a bed of crushed ice. A small amount is spooned over each oyster before eating. The acidity cuts through the creamy, briny texture of the oyster, creating a balanced and refreshing bite. 
For those looking to buy this specific product, it would likely be available from a seafood market, a specialty food retailer, or online food purveyors.