Name an example of a cooked emulsified dressing.

Hollandaise sauce is an example of a cooked emulsified dressing because it is made by combining egg yolks with melted butter and typically a small amount of an acid, such as lemon juice or vinegar, while it is gently heated. This process creates a stable emulsion that is rich and creamy. The technique of whisking the ingredients together over low heat allows for the emulsification to form, which is characteristic of this type of sauce.

In contrast, the other options mentioned either involve no cooking or are not primarily emulsified dressings. Ranch dressing and blue cheese dressing are typically made as cold emulsions with dairy ingredients, while vinaigrette is an uncooked emulsion of oil and vinegar or another acid, usually prepared at room temperature. Therefore, Hollandaise stands out as a classic example of a cooked emulsified dressing due to its unique preparation method and the use of heat in its creation.