Preparation of Meatloaf

1. Preheat your oven to 375°F and grease a 9 by 13 inch baking dish.
2. In a large bowl, whisk together the egg, milk, ketchup, Worcestershire, salt, pepper, and optional seasonings.
3. Stir in the minced onion and garlic until evenly dispersed.
4. Add the ground beef and breadcrumbs, then use clean hands or a fork to mix gently.
5. Press the mixture into the baking dish, making an even layer.
6. Make a shallow channel around the edges to prevent juices from overflowing.

Mashed Potato Preparation

1. Place the peeled, cubed potatoes in a pot of cold salted water and bring to a boil.
2. Cook until very tender, about 12 to 15 minutes, then drain well.
3. Return the potatoes to the hot pot to let steam escape for a minute.
4. Add butter, milk, and sour cream, then mash until creamy.
5. Stir in half of the cheddar and all the chives, then season with salt and pepper.
6. If using bacon, fold it into the potato mixture now.

Assembling the Casserole

1. Par bake the meatloaf base for about 20 minutes.
2. Gently spread the mashed potatoes over the meatloaf, sealing the edges.
3. Sprinkle the remaining cheddar over the potatoes.
4. If desired, brush a thin layer of ketchup over the meatloaf before adding potatoes.

Baking

1. Return the pan to the oven and bake for another 20 to 25 minutes until the potatoes are hot and cheese is melted.
2. Check the internal temperature of the meatloaf, ensuring it reaches 160°F.
3. Rest the casserole for 10 minutes before slicing to allow the layers to settle.