The béarnaise is a refined sauce of French origin - it was born in 1830 in a restaurant in Saint-Germaine en-Laye - which is used to accompany grilled red meats. Béarnaise sauce belongs to the category of hot emulsified sauces and is prepared with hot whipped egg yolks (in a container placed in a bain-marie with simmering water) on a base of restricted flavored vinegar. Then add some butter into small pieces and beat the sauce for a long time until it becomes frothy and velvety. It is very important that the heat is minimal otherwise the sauce can "go crazy".