Step 1: Heat olive oil in a large pot or Dutch oven over medium-high heat. Add ground beef and chopped onion. Cook, breaking up the beef with a spoon, until browned and onions are softened, about 6-8 minutes. Drain any excess grease.
Step 2: Stir in minced garlic, Italian seasoning, and red pepper flakes (if using). Cook for 1 minute until fragrant.
Step 3: Pour in the beef broth and bring to a boil. Add the bowtie pasta, ensuring it's mostly submerged. Reduce heat to medium, cover, and simmer for 10-12 minutes, or until the pasta is al dente, stirring occasionally to prevent sticking.
Step 4: Once pasta is cooked, reduce heat to low. Stir in the heavy cream and softened cream cheese until the cream cheese is fully melted and incorporated into the sauce.
Step 5: Add the shredded cheddar and mozzarella cheeses, along with the unsalted butter. Stir continuously until all the cheese is melted and the sauce is smooth and creamy. Season with salt and freshly ground black pepper to taste.
Step 6: Remove from heat and let sit for a few minutes to allow the sauce to thicken slightly. Garnish with fresh chopped parsley before serving hot.