Emulsion sauces are stable because the egg yolks they are made with contain natural emulsifiers.
Egg yolks are whisked into a reduction of vinegar, water and crushed peppercorns over a gentle heat until thick and creamy. Then, melted butter is gradually whisked in.
It is served warm with hot fish, boiled or steamed vegetables, and poached eggs. A well known dish featuring hollandaise sauce is eggs benedict.
Béarnaise sauce is made in the same way as hollandaise sauce but it contains herbs. Tarragon is part of the reduction and more fresh tarragon and chervil are added after the melted butter. More egg yolks are used than in hollandaise, resulting in a thicker sauce.
Béarnaise sauce is served warm with grilled meat, vegetables and grilled and pan fried fish.
Sabayon sauce is a light frothy sauce traditionally made with egg yolks, sugar and wine. The yolks are whisked with sugar until light, then wine is added and the mixture is whisked until it thickens over a bain marie. It is served as an accompaniment to many desserts. In Italy, where it originated, it is made with Marsala wine and served as a dessert in its own right (Zabaglione).
Unsweetened sabayon, made with egg yolks and water, is used in savoury dishes for glazing the finished dish under the grill. It is also added to sauces to lighten them.