Preheat oven to 350F/180C/Gas Mark 4. Heat the oil over medium heat and add onion, garlic and rosemary and cook for 5 mins. Add the kale and stock and bring to boil. Reduce the heat and simmer for 6-8 mins, until kale is tender but not discoloured. In a bowl, mix the turkey, egg, spring onion, parsley and cheese. Form into 2.5cm balls and put in a lightly oiled baking dish and bake for 10 mins. Add meatballs to soup and simmer, partially covered, for 5 mins.