Which sauce in French cuisine is most commonly made using a roux as a base?

Béchamel is a classic French sauce made using a roux as its base, specifically a white roux, which consists of equal parts flour and fat (usually butter) cooked together. The roux is then combined with milk, resulting in a smooth, creamy sauce that serves as a foundation for many dishes, such as lasagna, mac and cheese, or as a base for cheese sauce.

Understanding the preparation of Béchamel is essential, as it highlights the importance of mastering the roux technique in sauce-making, which provides both flavor and thickening properties. This foundational skill can be applied to several other sauces, establishing Béchamel as one of the "mother sauces" in classical French cuisine.

In contrast, other sauces listed, such as Hollandaise, Velouté, and Tomato sauce, have different preparation methods. Hollandaise is an emulsion made from egg yolks, butter, and lemon juice; Velouté is made by thickening stock with a roux, but is categorized separately due to its specific use of stock instead of milk; and Tomato sauce is based on tomatoes rather than a roux. Each of these sauces showcases unique techniques and ingredients that highlight the diversity in classic French cuisine, but B