Step 1: Preheat your oven to 375°F (190°C). Lightly grease a loaf pan (9x5 inches) or a 9x13 inch baking dish if you prefer a free-form loaf. In a large mixing bowl, gently combine the ground beef, eggs, breadcrumbs, minced onion, minced garlic, 1/4 cup ketchup (or BBQ sauce), Worcestershire sauce, Dijon mustard, 1/4 cup milk, Italian seasoning, salt, and pepper. Use your hands to mix just until everything is combined; overmixing can lead to a tough meatloaf.
Step 2: Firmly press the meat mixture into your prepared loaf pan or shape it into an even loaf on the baking dish. If you like, spread an additional thin layer of ketchup or BBQ sauce over the top for a lovely glaze. Bake for 50-60 minutes, or until the internal temperature reaches 160°F (71°C) when measured with a meat thermometer. Once baked, remove from the oven and let it rest for 10 minutes.
Step 3: While the meatloaf is baking, peel and cut your potatoes into uniform 1-inch chunks. Place them in a large pot, cover with cold, salted water, and bring to a boil. Reduce the heat and simmer until the potatoes are fork-tender, which usually takes about 15-20 minutes.
Step 4: Drain the cooked potatoes thoroughly. Return them to the hot pot or transfer them to a large mixing bowl. Add the warm milk (or cream), softened butter, salt, pepper, and garlic powder (if using) to the drained potatoes. Mash with a potato masher or use a hand mixer until smooth and creamy.
Step 5: If your meatloaf was baked in a loaf pan, carefully drain any excess fat before proceeding. You can transfer the meatloaf to a clean baking dish at this point if desired. Evenly spread the creamy mashed potatoes over the top of the rested meatloaf, ensuring the entire surface is covered. Generously sprinkle the shredded sharp cheddar cheese over the mashed potatoes.
Step 6: Return the dish to the oven for an additional 10-15 minutes, or until the cheese is beautifully melted, bubbly, and lightly golden brown. Allow the ultimate comfort dish to cool for a few minutes before slicing and serving. Enjoy every savory, cheesy bite!