How to Make It
Preheat the oven to 400°. In a medium skillet, heat the oil. Add the onion, carrots, celery and garlic and cook over moderate heat, stirring occasionally, until softened, about 8 minutes. Scrape the mixture into a very large bowl and let cool. Add the panko, eggs, mustard, ketchup, Worcestershire sauce, Tabasco, 1 1/2 tablespoons of salt and 1 teaspoon of pepper and stir to form a paste. Using your hands, work in the ground meats and cheese until combined.
Line a large roasting pan with parchment paper. Firmly pat the meat mixture into 2 loaves, about 10 inches long. Arrange the loaves 3 inches apart on the parchment and roast in the lower third of the oven for about 1 hour, until lightly browned and an instant-read thermometer inserted in the center of the loaves registers 150°. Let the meat loaves rest for 15 minutes, then cut into thick slices and serve with the Creamy Onion Gravy.