Mix until the onion and parsley are evenly distributed.
Transfer the meat to the prepared baking sheet.
Shape it by hand into an oblong loaf.
Baking
Bake for 30 minutes.
Remove the baking sheet from the oven.
Spread the half of the glaze meant for coating over the entire top of the meatloaf.
Return to the oven for 20 to 30 minutes, until a thermometer inserted into the center of the loaf reads 71°C.
Resting and Serving
Let the meatloaf rest for 5 to 10 minutes before slicing.
While it rests, spoon off the whitish juices (coagulated proteins) that have collected around the meat.
Transfer the meatloaf to a serving platter.
Cut into slices.
Serve with the reserved glaze on the side.
Notes
Meat: this recipe uses ground round, but chuck works too. In France, avoid 5% fat ground beef, which is too lean: the meatloaf turns out dry and dense. Choose 15% fat, or cut the beef with a little ground pork. In Germany, gemischtes Hackfleisch (half beef, half pork) works well. You can also use a mix of beef and pork, or beef and veal, or 10% fat ground beef for a slightly lighter version.Salt: this recipe uses Diamond Crystal kosher salt, which is much less salty by volume than table salt, hence the half teaspoon of table salt as a substitute.Horseradish: you'll find it in jars in the condiment aisle (Meerrettich in Germany). It gives the glaze a spicy kick. If you don't like horseradish, you can replace it with bourbon for a smokier flavor. Worcestershire sauce (Lea & Perrins) is available in most European supermarkets. European ketchup is a little less sweet and more acidic than American ketchup.Loaf pan or baking sheet: you can bake the meatloaf in a loaf pan, but it's better to shape it by hand on a baking sheet, because that makes it easier to remove the juices that run out during baking. For mini meatloaves, divide the mixture into 6 to 8 small loaves and bake for 20 to 25 minutes depending on their size. A 900 g loaf generally takes 45 to 60 minutes to cook: a thermometer reading of 71°C in the center is still the best guide.Other variations: add dried herbs or spices (oregano, basil, thyme, onion powder, garlic powder); blitz fresh bread into fine crumbs so it mixes in more easily; replace the bread with rolled oats (quick or old-fashioned, never steel-cut), panko breadcrumbs or crushed crackers, well soaked; replace the milk with a plant-based milk; use gluten-free bread and gluten-free Worcestershire sauce.Make ahead: the raw mixture keeps for one day in the refrigerator, in the bowl covered with plastic wrap. Take it out about 20 minutes before baking, then shape the loaf.Storage: leftovers keep for up to 5 days in the refrigerator, tightly wrapped or in an airtight container. Reheat slices in the microwave for 30 to 45 seconds, or wrapped in aluminum foil in a 150°C oven for 10 to 15 minutes. Cooked meatloaf can be frozen for 3 months, double-wrapped; uncooked meatloaf can be frozen for 2 to 3 months and must be thawed completely before baking and glazing as in the recipe.