Preheat and prep: Heat the oven to 375°F (190°C).
Grease a 9x13-inch baking dish with nonstick spray or butter. Set aside.
Cook the pasta: Boil in salted water until just shy of al dente, about 1–2 minutes less than package time. Drain and set aside. Don’t overcook—it will finish in the oven.
Brown the turkey: In a large skillet, heat olive oil over medium-high.
Add ground turkey and cook, breaking it up, until no longer pink and lightly browned, 5–7 minutes. Season with a pinch of salt and pepper.
Sauté aromatics: Reduce heat to medium. Add onion and cook until soft and translucent, 3–4 minutes.
Stir in garlic and cook 30 seconds until fragrant.
Build the sauce: Sprinkle ranch seasoning over the turkey mixture. Stir in chicken broth and milk. Simmer gently for 2–3 minutes to thicken slightly.
Make it creamy: Remove from heat.
Stir in Greek yogurt or sour cream, cream cheese (if using), and smoked paprika. Taste and season with additional salt and pepper if needed.
Add veggies and pasta: Fold in frozen peas or mixed veggies (no need to thaw) and the cooked pasta. Mix until evenly coated.
Layer the cheese: Transfer everything to the prepared baking dish.
Top with cheddar and mozzarella, spreading evenly.
Bake: Bake uncovered for 18–22 minutes, until the cheese is melted and bubbly and the edges are lightly golden.
Rest and garnish: Let the casserole rest for 5–10 minutes to set. Sprinkle with chopped parsley or chives. Serve warm.