Which type of sauce is made by thickening a liquid with roux?

The correct answer is velouté sauce. Velouté is one of the mother sauces in classical French cuisine and is defined by its preparation method, which involves thickening a light stock, such as chicken, fish, or vegetable stock, with a roux. A roux is made by cooking equal parts flour and fat (typically butter) together, which serves as a thickening agent when added to liquids.

This technique forms the basis of velouté, allowing for the creation of a smooth and flavorful sauce that can be further enhanced with seasonings or additional ingredients. Velouté can serve as the foundation for various derivative sauces, showcasing its versatility in culinary applications.

In contrast, béchamel sauce, another mother sauce, is made using milk thickened with a roux but does not involve stock. Hollandaise sauce is emulsified rather than thickened with a roux, primarily using egg yolks and butter to create a rich, creamy consistency. Tomato sauce is typically prepared through a reduction of tomatoes, seasoning, and other ingredients, rather than involving a roux for thickening.