Add butter to a saucepan and heat over medium heat until melted.

Once butter has melted, add the flour and whisk until mixture begins to bubble and foam. Continue to whisk for another 1 minute.

Slowly pour in the beef stock while whisking constantly.

Once stock is incorporated, whisk in the ketchup, Worcestershire sauce, salt and pepper.

Allow gravy to reach a boil. Meanwhile, combine cornstarch and water to make a slurry.

Once gravy begins to boil, add cornstarch slurry and whisk to combine.

Turn the heat down to medium-low and allow gravy to simmer until the mixture begins to thicken, it should coat the back of a spoon. About 10-15 minutes. Taste the sauce and adjust the seasonings to your liking.