In the same Dutch oven, melt 1 tablespoon of butter over medium-high heat. Add the mushrooms and cook, stirring regularly, until golden and tender, about 5 minutes. Add the remaining 1 tablespoon of butter, garlic, rosemary, and thyme; cook for 1 more minute.
Reduce the heat to medium. Add the flour and cook, stirring constantly, for 1 minute. Very gradually whisk in the beef broth, stirring constantly. Bring the liquid to a gently simmer, and then continue to cook, stirring, until the gravy thickens to your liking, about 2 minutes (remember that it will continue to thicken as it cools). Taste and season with salt and pepper if necessary.
Return the pork chops to the Dutch oven. Spoon the gravy over the top of the chops. Serve the pork chops and gravy over mashed potatoes and garnish with fresh herbs, if desired.