Preheat and prep: Heat the oven to 400°F (200°C). Line a sheet pan with foil and lightly oil it, or use a standard 12-cup muffin tin and spray with cooking spray.
Make the panade: In a large bowl, combine breadcrumbs and milk. Let sit 2–3 minutes to soften.
This keeps the meatloaf moist.
Add aromatics: Stir in grated onion, garlic, ketchup, Worcestershire, mustard, salt, pepper, smoked paprika, and parsley.
Mix in the meat: Add ground beef. Use your hands or a fork to gently mix until just combined. Do not overmix or the meatloaves will be tough.
Shape: Divide mixture into 8 equal portions. Shape each into a small oval loaf and place on the sheet pan, or press into 8 muffin cups, leaving a little space at the top.
Glaze: Stir together ketchup, brown sugar, mustard, and Worcestershire.
Spoon or brush a generous layer over each mini meatloaf.
Bake: Cook for 18–22 minutes, until the centers reach 160°F (71°C) on an instant-read thermometer. Muffin tin versions may cook a minute or two faster.
Rest and serve: Let rest 5 minutes. Spoon any juices over the tops, then serve with your favorite sides.