Step 1: Add the Meatballs - Place the frozen homestyle meatballs directly into a 6 quart slow cooker. There is no need to thaw them first, which is one of the reasons I like keeping a bag of meatballs tucked in the freezer for nights when the dinner plan never quite happened. Spread them into an even layer as much as you can so the sauce can work its way around them while everything cooks.
Step 2: Add the Butter and Garlic - Arrange the sliced butter over the frozen meatballs, then sprinkle the minced garlic evenly across the top. As the slow cooker warms, the butter will melt down around the meatballs and carry that garlic into the sauce. You do not need to stir yet. Just distribute everything fairly evenly and let the slow cooker take it from there.
Step 3: Mix the Cream Cheese Sauce - In a bowl, whisk the softened cream cheese with the chicken broth until the mixture is as smooth as you can get it. A few small cream cheese pieces are completely fine because they will soften as they cook. Stir in the Italian seasoning, garlic powder, onion powder, and black pepper. Pour this mixture evenly over the meatballs, making sure some of it reaches down between them.
Step 4: Let the Meatballs Cook - Cover the slow cooker and cook the meatballs on LOW for 4 to 5 hours or on HIGH for 2 to 3 hours. If you happen to walk through the kitchen and remember, give everything a gentle stir once or twice. If you are busy and forget, do not worry about it. The meatballs will continue cooking and the cream cheese will gradually soften into the broth.
Step 5: Stir the Sauce Smooth - About 30 minutes before you plan to serve dinner, remove the lid and give the sauce a thorough but gentle stir. By now the cream cheese should be very soft, and stirring helps pull the butter, broth, cream cheese, garlic, and seasonings together. Do not panic if it looked a little uneven earlier in the cooking process. This is the point where the sauce starts looking much more like the creamy Alfredo you were expecting.
Step 6: Add the Heavy Cream - Pour in the heavy cream and gently stir until it is incorporated throughout the sauce. Adding the cream toward the end protects its smooth texture and keeps it from spending hours exposed to heat. The sauce should already smell buttery and garlicky, and the cream will make it look noticeably silkier almost immediately.
Step 7: Melt in the Parmesan - Add the freshly grated Parmesan a handful at a time, stirring gently after each addition. Give each handful a chance to melt before adding the next. This takes a few extra minutes, but it helps you get a smoother sauce rather than one big clump of cheese. Freshly grated Parmesan really matters here because packaged shredded cheese often contains ingredients that keep the shreds separate in the bag, which can also keep them from melting smoothly.
Step 8: Finish the Alfredo Sauce - Cover the slow cooker again and cook on LOW for another 15 to 20 minutes. You are only trying to warm the cream and finish melting the cheese, so there is no need for a long final cooking time. When you open the lid, the sauce should look hot, creamy, and thick enough to cling to each meatball.
Step 9: Coat and Serve - Give the meatballs one final gentle stir so every one gets covered in the Alfredo sauce. Sprinkle the chopped parsley over the top and finish with additional Parmesan. Spoon the meatballs and plenty of sauce over pasta, potatoes, rice, or whatever sounds good that night. Make sure you get some sauce onto every plate because that is the part everybody will be scraping up at the end.