Preheat the oven to 375°F.

Spray a lined baking sheet with the cooking spray.

In a large bowl, combine the beef, pork, onion, breadcrumbs, ½ cup tomato sauce, eggs, Worcestershire sauce, 2 tablespoon balsamic vinegar, thyme, parsley, cheese, salt, and pepper.

Mix all the ingredients with clean hands until fully mixed.

Rinse a loaf pan (8" x 4") with water and then pack the meat mixture into the wet pan.

Invert the pan over the greased baking sheet and gently transfer onto the sheet.

Bake for 50 minutes.

Meanwhile, mix 3 tablespoon tomato sauce with 1 tablespoon balsamic vinegar. Set aside.

After 50 minutes, remove the meatloaf from the oven and brush the tomato/balsamic sauce over the top of the loaf and return to the oven to bake for another 20 minutes. Save some of the sauce for another brushing after the meatloaf has finished cooking.

In a large skillet, melt the butter over medium-high heat.

Add the shallots and cook until soft, about 2 to 4 minutes. Add the garlic and cook for another 1 minute.

Add the mushrooms and Worcestershire sauce and cook, uncovered, stirring occasionally, until lightly browned and have released their liquids, about 8 minutes.

Whisk in the flour and stir to coat. Cook for 3 to 4 minutes.

Add the balsamic and then the stock. Use a whisk to incorporate the flour into the liquid. Slowly simmer and stir until thickened, about 4 to 5 minutes.

Season with salt and pepper. Keep warm over low heat.

Transfer the meatloaf to a platter and slice.

Drizzle the gravy over the top. Garnish with chopped parsley, if desired.

Serve at once, passing the leftover gravy at the table.