Preheat oven to 350°F.
Sprinkle pork chops evenly on both sides with ranch dressing mix, salt, and pepper.
Heat oil in a large cast-iron skillet over high heat until smoking.
Add pork chops, and cook, turning occasionally, until lightly browned around the edges, about 8 minutes.
Transfer pork to a plate, reserving drippings in skillet; do not wipe skillet clean.
Reduce heat to medium-high.
Melt butter in drippings in skillet.
Add onion, and cook, stirring often and scraping up any browned bits on bottom of skillet, until onion softens slightly, about 4 minutes.
Remove skillet from heat.
Whisk together pepperoncini liquid, beef stock base, and ½ cup water in a small bowl.
Return pork to skillet; add pepperoncini peppers and liquid from jar mixture.
Bake in preheated oven until a thermometer inserted into thickest portion of pork registers 140°F, 10 to 12 minutes.
Transfer pork to a large platter, reserving gravy mixture in skillet.
Bring gravy mixture to a simmer over medium-high.
Whisk together cornstarch and ¼ cup water in a small bowl.
Stir cornstarch mixture into gravy.
Cook over medium-high, stirring often, until thickened, about 2 minutes.
Stir in herbs.
Spoon over pork chops; sprinkle with additional herbs.
