Step 1: Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
Step 2: In a small bowl, soak the Panko breadcrumbs in the milk for about 5 minutes until fully absorbed.
Step 3: Sauté the diced onions and minced garlic in a pan with a little butter until soft and translucent, then let cool slightly.
Step 4: In a large bowl, combine the beef, soaked breadcrumbs, sautéed onions/garlic, eggs, parsley, Worcestershire sauce, salt, and pepper.
Step 5: Mix gently with your hands until just incorporated, being careful not to overwork the meat.
Step 6: Shape the mixture into a 9x5-inch loaf on the prepared baking sheet.
Step 7: In a small bowl, whisk together the ketchup, brown sugar, and mustard. Spread half of this glaze over the loaf.
Step 8: Bake for 40 minutes, then apply the remaining glaze and bake for an additional 15-20 minutes until the internal temperature is 160°F.
Step 9: Remove from the oven and let rest for 10 minutes before slicing and serving.