Preheat your oven to 375°F (190°C).
In a large bowl, mix ground beef, breadcrumbs, milk, eggs, onion, garlic, ketchup, Worcestershire sauce, salt, and pepper until well combined.
Transfer the meat mixture to a loaf pan and shape into a loaf. Bake uncovered for 60 minutes or until the internal temperature reaches 160°F (71°C).
While the meatloaf bakes, heat olive oil in a skillet over medium heat. Add mushrooms and sauté until browned, about 6–8 minutes.
Add butter to the skillet. Once melted, sprinkle in the flour and stir to coat the mushrooms.
Gradually whisk in the beef broth and cook until the gravy thickens, about 5–7 minutes.
Stir in heavy cream if using, and adjust seasoning with salt and pepper to taste.
Remove the meatloaf from the oven, let it rest for 10 minutes, then slice and serve with the mushroom gravy.