Gramma Pandolfi's Pasta Sauce with Meatballs

Heat oil in a large stockpot over medium. Add onion, garlic, and mushrooms and cook, stirring occasionally, until soft, 6 –8 minutes. Crumble sausage, beef, and pork with your fingers into onion mixture. Add kosher salt, pepper, celery salt, oregano, garlic powder, and onion powder and cook, breaking up meat with a wooden spoon, until browned and cooked through, 3 –5 minutes. Add tomato paste and cook, stirring occasionally, 15 minutes. Add crushed tomatoes and tomato sauce. Stir to combine, then reduce heat to medium-low and simmer, stirring occasionally, at least 3 hours and up to 8.