Make the Meatballs: In a large bowl, combine the ground chicken, panko breadcrumbs, egg, Parmesan, 1 teaspoon granulated garlic, 1 teaspoon onion powder, 1 teaspoon Italian seasoning, ½ teaspoon salt, and ¼ teaspoon pepper. Mix gently until just combined, being careful not to overmix.
Using a medium cookie scoop or two spoons, form into 1½-inch balls (you should get about 18-20 meatballs).
Make the Sauce: Whisk together the chicken broth, sun-dried tomatoes, garlic, ½ teaspoon Italian seasoning, ½ teaspoon salt, and ¼ teaspoon pepper in a medium bowl.
In a separate small bowl whisk together the cornstarch and water. Add the cornstarch slurry to the sauce, whisking to combine.
Cook: Carefully nestle the meatballs into a 5- or 6-quart slow cooker in a single layer. Pour the sauce evenly over the meatballs.
Cover and cook on high for 2½ to 3 hours, or low for 4 to 5 hours, or until the meatballs are cooked through (165°F internal temperature) and tender.
Gently remove the cooked meatballs to a plate and set aside.
Add the Gnocchi: Switch the slow cooker to high if it isn't already. Add the gnocchi and cream, gently stirring to submerge. Cover and cook on high for 20 to 25 minutes until the gnocchi are tender and the sauce has thickened (resist the urge to lift the lid, the gnocchi need the steady heat).
Finish: Turn off the heat and stir in the Parmesan. Add the baby spinach and stir gently until wilted, about 2 minutes. Add the meatballs back in, stirring gently to combine, and allow to sit for 1-2 minutes to warm back through.
Taste for seasoning and adjust with salt and pepper as needed.