1. Gather all ingredients for the meatloaf, including lean ground beef, garlic pork sausage, Panko crumbs, beaten eggs, black pepper, tarragon, diced onion, sliced mushrooms, Swiss cheese, and uncooked applewood smoked bacon.
2. Preheat your oven or prepare your Dutch oven by setting the temperature to 350 degrees Fahrenheit.
3. In a large mixing bowl, combine the ground beef, garlic pork sausage, Panko crumbs, beaten eggs, black pepper, and tarragon. Mix gently but thoroughly to evenly distribute the ingredients without overmixing to prevent toughness.
4. Lay out a sheet of wax paper on your counter and place the meat mixture onto it. Press it into a rectangular shape approximately one inch thick.
5. Lay slices of Swiss cheese evenly over the meat mixture so that they completely cover the surface.
6. Distribute the diced onions and sliced mushrooms evenly over the layer of Swiss cheese.
7. Use the wax paper to assist in gently rolling the meat mixture into a loaf. Ensure it is tight and compact while sealing the edges for a secure structure to retain the fillings.
8. Place the meatloaf seam side down into an oiled 12-inch Dutch oven or on a lined baking sheet if cooking in a conventional oven.
9. Lay the slices of uncooked applewood smoked bacon over the top of the loaf, slightly overlapping for full coverage and added flavor.
10. If cooking in a Dutch oven, arrange briquettes for even heat distribution and cook for about 1½ to 2 hours until the internal temperature of the meatloaf reaches 145 degrees Fahrenheit.
11. If using a conventional oven, bake the meatloaf at 350 degrees Fahrenheit for approximately the same amount of time or until the internal temperature reaches 145 degrees Fahrenheit.
12. Once cooked, allow the meatloaf to rest for 10 minutes before slicing. This allows the juices to redistribute throughout the loaf for better flavor and easier slicing.
13. Serve the Bacon Mushroom Swiss Cheese Meatloaf warm with your choice of sides, such as roasted vegetables or mashed potatoes, and enjoy its rich, smoky, and hearty flavors.