In a large, heavy-bottom sauté pan, heat 2 tablespoons of the oil over medium heat and add the onion, celery, marjoram, and thyme. Season with salt and pepper and cook until the vegetables are soft and translucent but not browned. Remove from heat and transfer to a large mixing bowl to cool.

Preheat the oven to 350˚F.

Once the vegetable mixture is cool, add the beef, veal, eggs, bread crumbs, and about 2 teaspoons salt and ½ teaspoon pepper and mix well. Use the remaining ½ tablespoon oil to grease a loaf pan and transfer the mixture to the pan, packing it down gently. Cover with foil and place the loaf pan on a sheet pan. Cook in the oven for 1 hour.

Remove the foil and spread the top of the meat loaf with the tomato paste. Continue to cook for another 30 to 45 minutes until the instant-read thermometer reaches 150˚F. Remove from the oven and let it rest.

While it rests, make the gravy. In a large pan, heat the butter until it foams. Add the diced mushrooms and cook over high heat until their juices evaporate. Add shallots and season with salt and pepper. Cook until the mushrooms are browned and shallots are translucent, about 3 to 5 minutes. Sprinkle flour over and stir well, cooking for about 2 minutes, then stir in stock. Whisk to incorporate any stuck flour and add cream. Adjust seasoning as needed.

Serve the meat loaf in slices, with gravy ladled over or alongside, accompanied with mashed potatoes if desired.