Step 1

Heat the oven to 350°F. Arrange a rack in the bottom third of the oven, and heat to 350°F. Line a rimmed baking sheet or other baking dish with aluminum foil.

Step 2

Soak the bread pieces in the milk. Combine the bread pieces and the milk in a small bowl. Let stand until the bread has broken down into a thick porridge, occasionally stirring and mushing the bread against the sides of the bowl. You can leave the crusts on the bread or trim them off before soaking; if you leave them on, remove any large pieces that haven't broken down after soaking.

Step 3

Cook the veggies. Heat a few teaspoons of olive oil in a skillet over medium heat until shimmering. Add the diced onions, carrots, and celery. Cook until the onions are translucent and the carrots have softened, 6 to 8 minutes. If the vegetables begin to brown, turn down the heat. Add the garlic and stir until fragrant, about 30 seconds. Add the thyme and tomato paste, and stir until coated. Remove from heat and let cool slightly.

Step 4

Make the meatloaf mix. Place the ground meat, beaten eggs, Worcestershire sauce, salt and pepper, soaked bread and milk, and cooked vegetables in a large bowl. Working quickly, use your hands to work the ingredients together until just combined.

Step 5

Shape the loaf. Transfer the meatloaf mixture to the foil-lined baking sheet or baking dish. Shape it into a rough 9x5-inch loaf. (If using a loaf pan, just pat the meatloaf mixture into the pan.)

Step 6

Coat the loaf with ketchup or bacon (optional). Spread 1/4 cup of the ketchup mixture over the meatloaf (reserve the other 1/4 cup for later). Alternatively, drape the loaf with bacon slices.

Step 7

Bake for 45 minutes. Bake the meatloaf for 45 minutes.

Step 8

Bake for another 10 to 15 minutes. Spread the remaining 1/4 cup ketchup over the loaf. Bake until the middle of the loaf registers at least 155°F on an instant-read thermometer, 10 to 15 minutes more (about 1 hour total).

Step 9

Cool 15 minutes before serving. Let the loaf cool for at least 15 minutes before serving. If you baked the meatloaf in a loaf pan, carefully drain off the liquid fat before transferring the meatloaf to a clean cutting board. Cut into thick slices and serve.