Halve the onion lengthwise. Peel the papery skins off. Dice one half of the onion and set aside for later. Using the large holes on a box grater, grate the other half of the onion, discarding the root.
In a medium bowl combine grated onion, oatmeal, egg, ketchup, basil, salt, pepper, garlic and parmesan cheese. Stir until well combined. Add ground turkey and using your hands mix well until mixture is thoroughly combined.
Place a piece of parchment paper onto a rimmed baking sheet. Scoop out a small spoonful of turkey mixture and roll into one inch balls. (I used a small cookie scoop to achieve uniform meatballs). Bake meatballs for 15 minutes. Set aside to cool.
In a large dutch oven, add olive oil and heat over medium heat. Add the sliced mushrooms and saute until they give up their liquid and start to brown. Add the reserved, diced half of the onion, carrots, celery and garlic. Saute until vegetables are softened, about 5 minutes.
Add chicken stock and bay leaf and heat the broth to a boil. Reduce heat to simmer and add beans, tomatoes, meatballs, red pepper flakes and parmesan rind (if using). Simmer for 20 minutes. Stir in the kale and orzo and simmer for an additional 10 minutes or until orzo is cooked and kale is tender.
Sprinkle with parmesan cheese and fresh basil, if desired. Serve with croutons to sprinkle on soup or crispy breadsticks on the side.
Notes
Store leftovers sealed in an airtight container in the refrigerator for up to 5 days.