Cook onion, carrot, celery, ground meats, beef stock, and bouillon cube on high heat in beef broth for about 30 minutes or until broth is reduced and the carrots, onions, and celery are soft.
When the stock has been reduced, add garlic and salt and cook for 10 minutes more. If using stock that contains salt, modify amount of added salt accordingly.
Add more beef broth, bring to boil, then reduce heat to simmer until most liquid is gone, about another 30 minutes or longer.
Add spices and stir and cook another 5 minutes.
Turn off heat and add bread crumbs and stir which should soak up remaining liquid and fat.
Brush with beaten egg, if desired. Cut steam vent. Bake in preheated oven for 20 minutes; remove foil and return to oven. Bake for an additional 15 to 20 minutes, or until golden brown. Let cool 10 minutes before slicing.