In a large skillet over medium-high heat, add bacon and cook until some are golden brown. Transfer to a plate lined with paper towels. Remove all the fat with a paper towel except for 1 tablespoon.

In the same pan over medium-low heat, add onion and carrot. Saute for 10 minutes. Add bacon and cook for 5 more minutes. Stir in both ground meat and cook until no longer pink. Season with salt and pepper. Add oregano, rosemary, garlic and tomato paste. Saute for 1 minute.

Pour 1½ cups broth. Scrap off the brown bits at the bottom of the pan. Add the diced tomatoes and some of the juice. Add ketchup and sugar. Season with salt and pepper. Cook until the tomatoes are almost melted, about 30 – 40 minutes.  

Meanwhile, bring a large pot of water (salted) to a boil over high heat. Add the spaghetti and cook until tender but still firm to the bite, stirring occasionally, about 9 to 10 minutes. Drain the pasta and set aside.

Preheat the oven to 450˚F (230˚C).

Back to the meat sauce, make sure the mixture doesn’t reduce too much. The sauce should not be too thick and too dry. It should be pretty liquidy. Reduce the heat to low. Stir in half of the parmesan cheese. Mix well. Remove ½ of the meat sauce to a medium bowl and set aside. Add the spaghetti to the skillet. Mix to combine.

Transfer the spaghetti to a medium baking dish. Scoop the set-aside meat sauce over. Top with mozzarella cheese slices and sprinkle with the rest of parmesan cheese. Bake in the oven until cheese is melted and golden brown, about 15 – 20 minutes. (If you have a broiler, you can do 7 minutes in 450˚F, then 3 minutes in broiler.)