Preheat oven to 350°F. Lightly coat a 13- x 9-inch rimmed baking sheet with cooking spray, and line with parchment paper; set aside.
Stir together milk, garlic, eggs, Italian seasoning, kosher salt, and 2 tablespoons of the Worcestershire sauce in a large bowl until combined. Stir in panko, Parmesan, onion, and beef until combined.
Transfer meatloaf mixture to prepared baking sheet; press into an even layer.
Stir together ketchup and remaining 1 tablespoon Worcestershire sauce in a small bowl until combined; evenly spread over meatloaf mixture.
Bake in preheated oven until a thermometer inserted into center registers 160°F, 30 to 35 minutes. Without removing meatloaf from oven, increase oven temperature to broil. Cook until glaze just starts to caramelize, 3 to 5 minutes. Remove from oven. Carefully pour fat from baking sheet into a heatproof container; discard when cooled. Let meatloaf stand 5 minutes before serving. Garnish with chives, if desired.
