This stage of the recipe is really important ... the beef stock in this French onion soup could be substituted for mushroom stock. If you don't have Madeira, you can use dry sherry, white vermouth ...
To make it, you really only need sour cream and dried onion soup dip mix (Lipton is generally preferred, but other brands can be swapped in). Scoop the sour cream into a bowl. Pour in the soup mix ...