In a large pot or pan, add in the sausage and beef over medium-high heat. Use a spoon to break up the meat into small pieces. Add in the onion and garlic and cook, stirring constantly, until the meat is browned and no pink remains. Drain off fat.
Reduce heat to medium; add in the sugar, Italian seasoning, salt, pepper, and parsley. Add in the tomato paste and stir to combine.
Pour in the diced tomatoes with their liquid, crushed tomatoes, and chicken broth. Stir well until combined; bring to a simmer, then reduce heat to low and simmer for at least 1 hour (ideally 4)
Use right away, refrigerate for later, or freeze for down the road!
Isn't this Bolognese sauce? Well, sort of, but not really. Bolognese sauce is meat based like this, but typically made with carrots, celery, wine and/or milk (which are not included here.) Marinara sauce is basically tomato sauce with herbs and onion. So this particular recipe is like a cross between the two!
Don't freak out over the sugar! Sugar, like salt, is a great ingredient that gives balance to food and helps with overall flavor. It is especially needed in a spaghetti sauce to help cut the acidity from the tomatoes.
The longer this simmers the better the flavor. Low and slow, friends.
It can be made ahead and kept refrigerated in an air-tight container for up to 3 days. You can further extend its shelf life by freezing it, covered in an airtight container, for up to 4 months.