Transfer pork to a cutting board and let rest for about 10 minutes.
While meat is resting, transfer skillet back to the stovetop and heat over MED/MED HIGH heat. There should be drippings in the skillet from cooking the pork, drain off some if needed, so that you have about 1/4 - 1/3 cup left… those add great flavor.
Add bourbon and use a wooden spoon to scrape the bottom of the pan, loosening any browned bits.
Pour in chicken stock, apple cider, mustard, salt, pepper, and onion powder, and bring to a low boil.
In a small mixing bowl, combine cold water and cornstarch and whisk together until smooth.
Pour cornstarch mixture into the boiling liquid, whisking as you add it.
Reduce heat to MED LOW and simmer, stirring often, until gravy has thickened to your liking.
Remove from heat and add cold butter, whisking as it melts into the gravy.