In a large bowl, combine the turkey, Parmesan, pesto, egg, breadcrumbs, garlic, salt, and pepper. Mix well (I find using my hands works most effectively) and then use a medium cookie scoop to form even sized meatballs. I scoop then shape in my hands and put on a large plate.
Once all the meatballs are formed, heat butter and olive oil in a skillet over medium heat. Add the meatballs and cook for 2-3 minutes per side, or until golden and cooked through. Remove from skillet and set aside.
In the same skillet, still over medium heat, add the minced garlic and cook about 30 seconds, until fragrant. Whisk in the sour cream until heated through.
Whisk the cornstarch and water together to make a slurry, then add that along with the chicken broth, pesto, lemon juice salt and pepper and stir until well-combined. Lower heat and simmer 5-7 minutes until smooth and slightly thickened, stirring often.
Add the meatballs back into the skillet, over medium heat again, and spoon the sauce over while the meatballs heat through for a couple of minutes. Serve with zoodles, your favorite pasta, or rice and plenty of that delicious sauce!