Heat butter in a Dutch oven over medium-low heat. Sauté diced onion, minced garlic, salt, and pepper until soft and fragrant.
Increase heat to medium, add ground beef (or beef and sausage), and cook until browned. Drain excess grease.
Add beef stock and marinara sauce. Bring to a boil, then reduce to a simmer.
Stir in heavy cream and ricotta cheese. Let simmer for 30–45 minutes, stirring occasionally.
Taste and adjust seasoning with salt and pepper.
Serve hot, garnished with ricotta, Parmesan, and fresh basil.