Put the butter in the pan and scrape up anything stuck to the pan as it melts.
Once melted, add in the chopped onion and cook them until translucent or soft.
Add in the beef broth, Worcestershire Sauce, Ketchup, Salt, and Pepper.
Bring to a simmer.
In a separate small bowl, mix together the cornstarch slurry until smooth.
Pour it into the gravy while whisking continuously. Turn off the heat as soon as it thickens.
Add the patties back into the gravy. Serve with mashed potatoes and green beans. Enjoy!