Take a medium pot and add all of the ingredients above except for the cornstarch slurry ingredients.
Whisk well and let boil on low/medium heat for about 10 minutes (without lid). Stir form time to time.
After 10 minutes mix together the cornstarch slurry.
Make sure the gravy is boiling when you add the cornstarch slurry. Whisk while adding it.
If you want the sauce even thicker, simply add more cornstarch slurry to it. But be careful, you don't want it to turn into jell-o.
Let the gravy boil lightly for another 10 minutes (without lid).