Step 1: Add the Meatballs to the Slow Cooker - 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 keep this recipe in mind for busy days. Spread them out into a fairly even layer so the sauce can work its way around them as they heat. If they are piled a little, that is completely fine. The slow cooker will still do its job.
Step 2: Melt the Butter and Wake Up the Garlic - Set a medium saucepan over medium heat and melt the butter. Add the minced garlic and cook it for about 30 seconds, stirring as it becomes fragrant. You are not trying to brown the garlic here. You just want to take away that raw edge and let the butter pick up all of its savory flavor. Once you can really smell the garlic, it is ready for the next ingredients.
Step 3: Whisk Together the Creamy Sauce - Add the cream of chicken soup, chicken broth, heavy cream, and crushed red pepper flakes to the saucepan. Whisk everything together until the mixture is smooth and creamy. It may seem a little loose at this stage, and that is exactly what you want. The sauce will thicken as the meatballs cook, and the Parmesan added near the end gives it even more body.
Step 4: Stir in the Sun Dried Tomatoes - Stir the chopped sun dried tomatoes into the warm sauce. I like chopping them into small pieces because it means nobody gets one giant chewy tomato on a fork. Instead, you get little tangy bites scattered throughout the entire meal. The tomatoes also add enough brightness to keep the creamy sauce from tasting too heavy.
Step 5: Pour the Sauce Over the Meatballs - Pour the sauce evenly over the frozen meatballs in the slow cooker. Use a spoon to gently move a few meatballs around if needed so the sauce can settle between them. Cover the slow cooker and cook on LOW for 4 to 5 hours or on HIGH for 2 to 3 hours. If you happen to be nearby, give everything a gentle stir about halfway through. If the afternoon gets away from you and you forget, dinner will still be fine.
Step 6: Melt in the Parmesan - During the final 15 minutes of cooking, stir in the freshly grated Parmesan cheese. Give it a minute or two to melt into the hot sauce, then stir again until everything looks creamy and smooth. Adding the Parmesan near the end keeps the sauce from becoming grainy and gives you that silky coating you want around every meatball.
Step 7: Fold in the Spinach and Finish - Add the chopped spinach and gently fold it into the sauce. Put the lid back on and let the spinach cook just until wilted, which should only take a few minutes in the heat of the slow cooker. Spoon the meatballs and plenty of sauce over your favorite side, then finish everything with chopped parsley and another sprinkle of freshly grated Parmesan. This is the point when my family usually starts hovering around the kitchen asking if dinner is ready.