Heat a large skillet to medium-high. Add ground beef, Italian sausage, onions, and garlic and cook until browned about 8 minutes. Drain fat and add sauce and diced tomatoes, and mix until combined.
Add a layer of meat sauce into the bottom of the slow cooker, then a layer of frozen ravioli, meat sauce, and cheese. Then repeat until you run out.
Cook on high for 3-4 hours or low 5-6 hours. Turn off the slow cooker and let set 20 minutes. Sprinkle with Parmesan cheese and fresh basil.
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Notes
You can use just Italian sausage or just ground beef.This recipe can easily be doubled for large families.