1. Preheat your oven to 375°F (190°C). Lightly grease a loaf pan or line a baking dish with parchment paper for easy cleanup.
2. In a large mixing bowl, combine the ground beef, finely chopped onion, minced garlic, breadcrumbs, egg, milk, shredded cheddar cheese, ketchup, Worcestershire sauce, dried thyme, salt, and pepper. Use your hands to mix everything gently until just combined—overmixing will make the meatloaf tough.
3. Transfer the meat mixture to the prepared pan, shaping it into a neat loaf. Sprinkle a little extra cheddar cheese on top for that golden, cheesy finish.
4. Bake the meatloaf in the preheated oven for 50-60 minutes or until the internal temperature reaches 160°F (71°C). Halfway through, baste the top with any juices from the pan to keep it moist.
5. While the meatloaf is baking, boil the peeled and chopped potatoes in salted water until tender—about 15-20 minutes. Drain well.
6. Return the drained potatoes to the pot or a large bowl. Add butter, shredded mozzarella cheese, and milk or cream. Mash everything together until smooth and creamy. Season with salt and pepper to taste.
7. Once the meatloaf is done, let it rest for 10 minutes before slicing. Serve with a generous scoop of the cheesy mashed potatoes on the side, and garnish with fresh parsley if you like.

I’ve found that letting the meatloaf rest is key—it helps the juices redistribute, so every slice is tender and juicy. Growing up, my grandmother always emphasized this step, and I promise it makes a difference!