Preheat oven to 350 degrees Fahrenheit. Spray a 9-inch x 5-inch loaf pan with cooking spray and line with parchment paper (the parchment paper should cover the bottom and two longest sides of the loaf pan, with some parchment paper slightly overhanging the longest sides — this makes for easy removal of the meatloaf after it's baked). Spray the parchment paper with cooking spray, then set aside.

In a small bowl, mix 4 tablespoons of ketchup with yellow mustard and brown sugar. Set aside.

In another small bowl, mix together the bread crumbs with milk and set aside.

Heat olive oil and butter in a skillet over medium heat. Add mushrooms and cook for 5 minutes without stirring, then continue to cook for another 3 to 5 minutes, stirring occasionally, until the mushrooms have softened and released some of their moisture. Transfer the mushrooms to a bowl to cool while you prepare the rest of the meatloaf mixture.

In a large mixing bowl, add the ground beef with the milk-soaked bread crumbs, remaining 2 tablespoons of ketchup, eggs, carrot, onion, Parmesan cheese, Worcestershire sauce, salt, black pepper, garlic powder, thyme, cayenne pepper and the cooked and cooled mushrooms. Mix until well combined.

Transfer the ground beef mixture to the prepared loaf pan, gently pressing in, and bake for 1 hour. Carefully remove the meatloaf from the oven and spread the reserved ketchup mixture over top (before spreading the meatloaf sauce over top, if there is liquid/juices on top of the meatloaf, you can pour it off or allow it to run back into the corners of the pan — my favourite thing to do is the latter because there is so much flavour in those juices). Place the meatloaf back into the oven and continue to cook for another 20 minutes or until the meatloaf is fully cooked through (the internal temperature reaches 165 degrees Fahrenheit in the centre of the meatloaf when checked with an instant-read meat thermometer).

Once cooked, carefully remove the meatloaf from the oven. Allow the meatloaf to cool in the pan for 5 minutes. Then remove the meatloaf from the pan and allow it to cool for another 10 to 15 minutes (this makes slicing much easier). Garnish with parsley if you like. Slice and serve. Enjoy!