Preheat the oven to 400 degrees. Line a baking sheet with foil and spray with non-stick cooking spray.
Next, in a medium bowl combine ground chicken, parsley, panko, Parmesan cheese, garlic, kosher salt, pepper and egg. Take about 1.5 tbsp of chicken mixture, form into a meatball and place on a prepared baking sheet. Repeat the process until all the chicken meatballs have been formed. Cook the meatballs for about 10 minutes or until an internal temperature of 165 degrees.
While the chicken meatballs are cooking, preheat a medium skillet and melt 1 tbsp unsalted butter over medium heat. Add the onion, celery, kosher salt, and pepper to the skillet. Cook until translucent and then add the spinach leaves. Cook the spinach leaves down until wilted and set the skillet aside.
Next, prepare the polenta according to package directions. Once cooked, stir in 1 tbsp unsalted butter, cream, parmesan cheese, and celery mixture. Stir to combine and then divide the polenta among four bowls. Top the polenta with chicken meatballs and enjoy!