In a large bowl, stir together breadcrumbs and milk (or sour cream); let stand to absorb. Line a baking sheet with parchment paper or aluminum foil. Preheat oven to 350ºF.
Heat oil in a large saucepan over medium heat, then cook onion with 1 tsp salt until softened, about 7 minutes. Add garlic and cook until fragrant, about a minute more. Cool for a few minutes, then scrape into breadcrumb mixture.
Stir 1/4 cup ketchup into the breadcrumb mixture, along with Worcestershire sauce, parsley, remaining salt, and the pepper. When mixture is cool to the touch, stir in the eggs then the ground meat. Use your hands to gently but thoroughly work the mixture together.
Scrape the meat mixture onto the prepared pan and use your hands to shape it into roughly 9x5" loaf shape. Dollop on the remaining 1/3 cup ketchup, using a spoon to spread it out evenly.
Bake in center rack of oven for about 1 hour, or until center reads 160ºF. Allow meatloaf to rest on pan for 10 minutes before slicing.