Drizzle two tablespoons of olive oil into a large skillet over medium heat. Add the onion and the garlic. Saute for 5-6 minutes, until tender but not brown. Add the chicken broth and the Worcestershire sauce, and cook for another 2 minutes. Remove from heat and let cool.
In a large bowl, gently mix the ground turkey with the rest of the meatball ingredients, including the sauteed onions and garlic. Do not overmix. Shape into 20 balls of equal size, about 1.5 inches in diameter.
To make the gravy, bring 2 cups of chicken broth to a boil in a saucepan. Add the cornstarch dissolved in cold water, followed by the Worcestershire sauce. Cook for a minute or so, until thickened. Set aside.
In a large non-stick skillet, heat the remaining tablespoon of olive oil and one tablespoon of butter over medium-high heat. Add the meatballs and cook, undisturbed, for 2 minutes or until browned. Flip and cook for another 2 minutes.
Pour the gravy over the browned meatballs, lower the heat to low, cover and cook for about 15-20 minutes, or until the meatballs reach 165F internal temperature.
Serve hot, over mashed potatoes, drizzled with the gravy from the pan, and garnished with minced parsley.