01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, combine ground turkey, breadcrumbs, egg, milk, parsley, grated onion, garlic, salt, and pepper. Mix until just incorporated.
03 - Shape mixture into 20–24 small meatballs and place evenly on the prepared baking sheet. Bake for 15–18 minutes until golden and cooked through.
04 - While meatballs bake, bring a large pot of salted water to a boil. Cook egg noodles according to package directions, then drain and set aside.
05 - In a large skillet over medium heat, heat olive oil and butter. Add sliced mushrooms and sauté until browned, about 5–6 minutes. Add diced onion and cook until softened, 2–3 minutes. Stir in garlic and cook 1 minute more.
06 - Sprinkle flour over sautéed vegetables, stirring well. Cook for 1 minute to eliminate raw flour flavor.
07 - Gradually whisk in chicken broth, then add Worcestershire sauce and Dijon mustard. Bring to a boil, reduce heat, and simmer until sauce thickens, about 5 minutes.
08 - Lower heat to low and stir in sour cream until smooth. Season with salt and black pepper to taste.
09 - Add baked meatballs to the skillet and gently simmer for 3–4 minutes to heat through.
10 - Plate egg noodles and spoon meatballs and sauce over them. Garnish with chopped fresh parsley.