Preheat the oven to 425°. Pull pork chops out of the refrigerator and let it rest and warm up before cooking.
Make the Filling:
Peel, core, and dice apple into small pieces. Dice bacon and shallot and grate cheddar on a cheese grater.
Preheat a large, oven-safe skillet over medium heat and add about a tablespoon of oil.
Add diced bacon and cook for a few minutes, until bacon fat is rendered about half way.
Add diced shallot and cook until almost all of the bacon fat is rendered. Add apples and season with a little salt and pepper. Cook everything until apples are softened and bacon fat is all rendered.
Take the filling mixture out of the pan but leave the grease in the pan.
Let the apple bacon mixture cool a little bit and stir in grated cheese.
To Stuff Pork Chops:
Place pork chop onto the cutting board and place your hand over it. Use a sharp knife to cut a pocket in the pork chop that is large but don't slice all the way through.
Stuff each pork chop with prepared stuffing and you can secure the opening with a toothpick.
Cooking Stuffed Pork Chops:
Use the same skillet where you prepared the filling to cook the meat.
Make sure to reheat the skillet over medium-high heat if it cooled down.
Place stuffed pork chops into the skillet and let it sear for a couple of minutes. Flip them over and let them sear for about a minute.
Transfer the skillet into the preheated oven and cook until internal temrpature reaches 145°. Since pork will continue to cook while resting, I pull them out when they reach 138°-140°.
Note: for the stuffed pork chops that are about 1 - 1¼ inch thick, it will take 15-18 minutes in the oven.
To Make the Sauce:
Prepare your ingredients before starting to cook.
Start cooking the sauce right after you pull the pork chops out of the oven, while they are resting.
Melt butter in a sauce pot over medium heat and add diced shallot. Cook shallots until completely softened and start to brown.
Sprinkle flour over the onion and stir. Once onions are coated in flour start to pour in chicken stock as you whisk continuously.
Add vinegar, mustard, maple syrup, sage, salt, and pepper. Whisk well until sauce is smooth and thickened.
Scoop out about 1/4 cup of juices that accumulated in the skillet from cooking pork and stir it into the sauce. (If you want the sauce even thinner, add some more juices from cooking pork.)