You can make chicken gravy by using chicken broth or beef gravy by using beef broth.
Saute the onion in the butter 5 minutes or so, until soft and translucent.
Stir in the flour and cook a few minutes, stirring constantly.
Add the vermouth or wine and 1/4 cup of the broth, stirring until smooth with a whisk. Slowly add the rest of the broth gradually, stirring. Let simmer another five minutes, stirring constantly. Stir in leftover pan drippings or another tablespoon of butter if you don't have any. Taste and season.
Goes great with beef hash.