Hollandaise sauce mayonnaise and Béarnaise, the egg does not coagulate as in a custard; rather, the lecithin in the eggs serves as an emulsifier, allowing the mixture of the normally immiscible butter and lemon juice to form a stable emulsion. To make hollandaise sauce, beaten egg yolks are combined with butter, lemon juice, salt, and water, and heated gently while being mixed. Some cooks use a double boiler in order to control the temperature. Some recipes add melted butter to warmed yolks; others call for unmelted butter and the yolks to be heated together; still others combine warm butter and eggs in
French cuisine and created new combinations and pairings. Some have speculated that a contributor to nouvelle cuisine was World War II when animal protein was in short supply during the German occupation. By the mid-1980s food writers stated that the style of cuisine had reached exhaustion and many chefs began returning to the haute cuisine style of cooking, although much of the lighter presentations and new techniques remained. There are many dishes that are considered part of French national cuisine today. A meal often consists of three courses, "hors d'œuvre" or "entrée" (introductory course, sometimes soup), "plat principal" (main course), "fromage" (cheese