Brown the Beef: Cook ground beef and diced onion in a skillet over medium heat until beef is no longer pink and onions are translucent, about 5-7 minutes. Break up any large chunks with a wooden spoon as it cooks. Drain excess fat to prevent the final dish from becoming greasy.

Build the Creamy Sauce: In your slow cooker, combine the Alfredo sauce, cream soup, beef broth, ranch seasoning, garlic powder, and black pepper. Whisk thoroughly until the mixture is smooth with no lumps of seasoning remaining. This creates the flavorful base that will infuse the entire dish.

Add the Beef: Add the cooked ground beef and onion mixture to the sauce in the slow cooker. Stir well to combine, ensuring the meat is evenly distributed throughout the sauce for consistent flavor in every bite.

Add the Tortellini: Pour the frozen cheese tortellini directly into the slow cooker. Gently fold the tortellini into the sauce mixture, making sure each piece is coated. The tortellini will cook to perfect tenderness in the sauce while absorbing all the delicious flavors.

Slow Cook: Cover the slow cooker and cook on LOW for 3-4 hours or on HIGH for 1½-2 hours. The tortellini should be tender but not mushy, and the sauce will have thickened slightly. Stir occasionally if possible to ensure even cooking.

Make It Extra Creamy: Once the cooking time is complete, stir in the shredded mozzarella cheese (and cheddar if using). Replace the lid and let sit for 5-10 minutes until the cheese is fully melted and incorporated into the sauce, creating an extra luxurious texture.

Garnish & Serve: Sprinkle dried parsley over the top for a touch of color and freshness. Serve warm in bowls, perhaps with garlic bread on the side to soak up the delicious sauce.