Preheat the oven to 375 degrees.

In a large bowl combine the eggs, milk, onion, garlic, tomato paste, balsamic vinegar, and Worcestershire sauce. Next, stir in the breadcrumbs, parmesan cheese, and Italian seasoning. Stir until just combined. Add the ground beef and, using your hands, combine everything together just until the breadcrumb mixture is well combined with the beef. Form the beef mixture into a loaf and press it into a 1.5-quart loaf pan. Bake it at 375 degrees for 45 minutes to 1 hour or until the internal temperature reads 165 degrees. Remove it from the oven and let it rest for at least five to ten minutes before slicing and serving.

To make the sauce, melt four tablespoons of the butter in a large pan over medium heat. Add the quartered mushrooms and let them cook until they are golden brown, about ten minutes. Pour in 1/4 cup of the balsamic vinegar and let it boil until the liquid has evaporated. Remove the mushrooms from the pan and set aside.

In that same pan, add 2 tablespoons of butter and let it melt. Ad the chopped mushrooms and let them cook in the butter for a few minutes. Add the beef stock and bring it all to a boil. Lower the heat and let it simmer for about 20-30 minutes until the beef stock is thick enough to lightly coat the back of a spoon. Turn off the heat and add the parsley and cream. Check for seasoning and add salt and pepper to taste (about 1/2 teaspoon of salt and 1/4 teaspoon of pepper to start).

Spoon the quartered mushrooms over the meatloaf slices before pouring a few tablespoons of the sauce over the top. Garnish with chopped parsley and grated Parmesan.