FATS AND OILS Fats make sauces palatable, and improve their flavour and texture. The ones usually used in sauces are "yellow" fats, such as butter or margarine, or oils. Many are combined with flour in sauces, for example in a roux, a cooked paste, or in beurre manie, a raw paste. Heating flour with fat allows liquid to be incorporated without forming lumps. The classic emulsified sauces, such as hollandaise or mayonnaise, use either melted butter or liquid oils, beaten with eggs until combined and thickened in an emulsion. The same principl is used in reduced sauces, such as beurre blanc, or in oil-based salad dressings such as vinaigrette, where the fat is whisked into a reduced or well-flavoured liquid base to make a smooth emulsion. In salsas and purées, oil is added for flavour by stirring into, or drizzling over, the other ingredients.