Recipes for onion soup vary greatly. Gently cooking sliced onions in butter or oil until softened and golden is the norm, but cooks differ about the cooking liquid. Beef stock is the most popular,{{refn|Beef stock is recommended by [[Simone Beck]], [[Louisette Bertholle]] and [[Julia Child]] in their ”[[Mastering the Art of French Cooking]]”, [[Robert Carrier (chef)|Robert Carrier]], [[Simon Hopkinson]], [[Thomas Keller]], [[Michel Roux Jr.]] and [[Nigel Slater]].<ref>Beck, Bertholle and Child, p. 42</ref><ref name=fc>Cloake, Felicity. “[https://www.theguardian.com/lifeandstyle/wordofmouth/2012/mar/22/how-to-cook-perfect-french-onion-soup “How to cook perfect French onion soup”], ”The Guardian”, 22 March 2012</ref>|group=n}} but some cooks specify chicken or veal stock or plain water.{{refn|[[Anthony Bourdain]] and [[Richard Shepherd]] specify chicken or alternatively (in Shepherd’s case) veal stock.<ref name=fc/><ref>Avila, p. 43</ref> [[Jean-Pierre Coffe]] recommends beef or chicken stock,<ref>Coffe, p. 86</ref> [[Auguste Escoffier]] calls for unspecified broth,<ref>Escoffier, p. 75</ref> and [[Marcel Boulestin]] and [[Raymond Blanc]] suggest only water;<ref name=fc/><ref>Boulestin, p. 54</ref> [[Paul Bocuse]] calls for either water or beef stock.<ref>Bocuse, p. 23</ref>|group=n}} Many cooks add alcohol to the cooking liquid, in the form of white wine, cider, [[calvados]] or brandy.<ref name=fc/> The cheese for the gratin is usually [[Gruyère]], [[Comté (cheese)|Comté]] or [[Emmental cheese|Emmental]].<ref>{{Cite web |title=Slow-Cooker French Onion Soup |url=https://food52.com/recipes/3238-slow-cooker-french-onion-soup |access-date=2025-09-09 |website=[[Food52]] |language=en}}</ref>{{refn|In America, mozzarella cheese is sometimes used as a variant.<ref name=bb>[https://bigglebit.com/which-cheese-french-onion-soup/ ” what cheese makes up French onion soup”], ”BiggleBit”, 3 Dec 2023</ref>|group=n}}
Recipes for onion soup vary greatly. Gently cooking sliced onions in butter or oil until softened and golden is the norm, but cooks differ about the cooking liquid. Beef stock is the most ,{{refn|Beef stock is recommended by [[Simone Beck]], [[Louisette Bertholle]] and [[Julia Child]] in their ”[[Mastering the Art of French Cooking]]”, [[Robert Carrier (chef)|Robert Carrier]], [[Simon Hopkinson]], [[Thomas Keller]], [[Michel Roux Jr.]] and [[Nigel Slater]].<ref>Beck, Bertholle and Child, p. 42</ref><ref name=fc>Cloake, Felicity. “[https://www.theguardian.com/lifeandstyle/wordofmouth/2012/mar/22/how-to-cook-perfect-french-onion-soup “How to cook perfect French onion soup”], ”The Guardian”, 22 March 2012</ref>|group=n}} but some cooks specify chicken or veal stock or plain water.{{refn|[[Anthony Bourdain]] and [[Richard Shepherd]] specify chicken or alternatively (in Shepherd’s case) veal stock.<ref name=fc/><ref>Avila, p. 43</ref> [[Jean-Pierre Coffe]] recommends beef or chicken stock,<ref>Coffe, p. 86</ref> [[Auguste Escoffier]] calls for unspecified broth,<ref>Escoffier, p. 75</ref> and [[Marcel Boulestin]] and [[Raymond Blanc]] suggest only water;<ref name=fc/><ref>Boulestin, p. 54</ref> [[Paul Bocuse]] calls for either water or beef stock.<ref>Bocuse, p. 23</ref>|group=n}} Many cooks add alcohol to the cooking liquid, in the form of white wine, cider, [[calvados]] or brandy.<ref name=fc/> The cheese for the gratin is usually [[Gruyère]], [[Comté (cheese)|Comté]] or [[Emmental cheese|Emmental]].<ref>{{Cite web |title=Slow-Cooker French Onion Soup |url=https://food52.com/recipes/3238-slow-cooker-french-onion-soup |access-date=2025-09-09 |website=[[Food52]] |language=en}}</ref>{{refn|In America, mozzarella cheese is sometimes used as a variant.<ref name=bb>[https://bigglebit.com/which-cheese-french-onion-soup/ ” what cheese makes up French onion soup”], ”BiggleBit”, 3 Dec 2023</ref>|group=n}}
