You need 2 to 2 1/2 kilos of cooked Italian meatballs, these can be party size (golf ball size) or larger dinner size. You have several options to do this. 1. You can use what ever meatball recipe you are familiar with. 2. Use the meatball recipe on this site, which can be made on the day you are making this recipe, or from frozen as it is a general make ahead type recipe, link is in Recipe Notes section. 3. Last resort, you can use store bought frozen meatballs. If using frozen meatballs, thaw them, if using fresh made AND cooked meatballs, they need to be cooled to room temperature.
In a large mixing bowl, add the soup (if using homemade from the short, it needs to be room temperature), sour cream, and water. Mix, then add the meatballs and mix those in to ensure all are coated well.
Refrigerate the meatballs and mixture overnight. this allows the meatballs to absorb the flavors.
The next day, pour the meatballs and mixture into your slow cooker and set to Low setting until the mixture is hot and the meatballs heated through.
If the meatballs did not soak overnight, heat on Low setting for a longer time, 3-5 hours so they can absorb the flavor and have a better taste to them.
For party size meatballs, serve as appetizers. For dinner size meatballs, I would serve over cooked pasta along with the sauce.