In a heavy skillet, melt 2 T butter. Cook onion and mushrooms until soft; about 5 minutes. Add garlic, cook for 1 minute.
Put onion/mushroom mixture into a large bowl and add parsley, egg, bread crumbs, and a bit of salt and pepper. Mix thoroughly.
Fill pockets in pork chops with filling and seal edges with toothpicks. Season chops with salt. Arrange in baking dish with a lid and bake, covered, until a good thermometer in the thickest part of the meat (not the filling) reaches 135 degrees, 40-35 minutes.
Remove the lid and place the chops under the broiler; cook until golden brown, about 4 minutes. Transfer chops to a serving platter to keep warm.
Set the pan on the stove, add about 1 pint of broth and cook until reduced by half.
Whisk in 1-2 T of roux slowly until you get the desired thickness for your gravy.