Step 1: Heat olive oil in a large, heavy-bottomed pot or Dutch oven over medium-high heat. Add ground beef and Italian sausage. Break up the meat with a spoon and cook until browned, about 8-10 minutes. Drain excess fat, leaving about 1-2 tablespoons in the pot.
Step 2: Add chopped onion and bell pepper to the pot. Sauté for 5-7 minutes, until softened and translucent. Stir in minced garlic and cook for another minute until fragrant.
Step 3: Stir in the tomato paste and cook for 2-3 minutes, stirring constantly, allowing it to deepen in color and flavor.
Step 4: Pour in the crushed tomatoes, beef broth, and Worcestershire sauce. Add Italian seasoning, oregano, basil, red pepper flakes (if using), salt, and black pepper. Stir well to combine. Bring to a simmer, then reduce heat to low, cover, and cook for at least 30 minutes, or up to an hour, stirring occasionally.
Step 5: While the sauce simmers, bring a large pot of salted water to a rolling boil. Add spaghetti and cook according to package directions until al dente, typically 8-10 minutes. Reserve about 1 cup of pasta water before draining.
Step 6: Drain the cooked spaghetti thoroughly.
Step 7: Once the sauce has simmered, taste and adjust seasonings if needed. If the sauce is too thick, add a splash of the reserved pasta water until it reaches your desired consistency.
Step 8: Add the drained spaghetti directly to the pot with the sauce. Toss everything together until the pasta is thoroughly coated.
Step 9: Serve the dirty spaghetti hot, garnished with freshly grated Parmesan cheese and fresh parsley. Enjoy this comforting dirty spaghetti recipe!