Preheat Oven & Prep Loaf Pan: Preheat your oven to 350°F (175°C). Lightly grease a 9x5 inch loaf pan.

Mix Meatloaf: In a large mixing bowl, gently combine the ground beef, breadcrumbs, milk, egg, chopped onion (½ cup), 2 tbsp ketchup, 1 tbsp Worcestershire sauce, garlic powder, dried thyme (½ tsp), salt (1 tsp), and black pepper (½ tsp). Use your hands to mix until just combined; do not overmix, or the meatloaf will be tough.

Form Loaf: Press the meat mixture evenly into the prepared loaf pan. If desired, spread an extra layer of ketchup over the top for a classic glaze.

Bake Meatloaf: Bake for 1 hour to 1 hour 15 minutes, or until the internal temperature reaches 160°F (71°C). Drain any excess fat from the pan. Let the meatloaf rest in the pan for 10 minutes before slicing.

Make Mushroom Gravy: While the meatloaf bakes and rests, prepare the gravy. In a large skillet or saucepan, melt 2 tbsp butter over medium heat. Add the sliced mushrooms and sauté for 5-7 minutes until they are softened and lightly browned. Add the ¼ cup finely chopped onion and minced garlic; cook for another 2-3 minutes until fragrant.

Thicken Gravy: Sprinkle the 2 tbsp all-purpose flour over the mushrooms and onions. Cook, stirring constantly, for 1 minute to create a roux. Gradually whisk in the 2 cups beef broth, 1 tbsp Worcestershire sauce, and ¼ tsp dried thyme. Bring to a simmer, whisking occasionally, until the gravy thickens to your desired consistency. It should be a beautiful, **thick, savory sauce**.

Season Gravy: Taste the gravy and season with salt and pepper as needed. Ensure it has a rich, umami flavor.

Serve: Slice the rested meatloaf and serve warm, generously spooning the **rich mushroom gravy** over each slice. Garnish with fresh thyme sprigs if desired.