Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente. Drain and set aside.
While the pasta cooks, heat olive oil or butter in a large skillet or deep saucepan over medium heat. Add the frozen peas, carrots, and corn. Sauté for 3–4 minutes until softened. Set the veggies aside.
2. Make the Sauce:
In the same skillet, melt 4 tbsp butter over medium heat. Add the chopped onion and garlic, cooking until softened (about 3 minutes).
Sprinkle the flour over the onion and garlic mixture, stirring constantly to form a roux. Cook for 1–2 minutes to eliminate the raw flour taste.
Gradually whisk in the chicken broth, making sure to avoid lumps. Add the heavy cream and stir until the sauce thickens, about 5–7 minutes.
Stir in the thyme, rosemary, garlic powder, salt, and pepper. Adjust seasoning to taste.
3. Combine Everything:
Add the cooked pasta, sautéed veggies, and shredded chicken to the skillet with the sauce. Stir well to coat everything evenly.
4. Optional Topping (For a Baked Version):
Preheat your oven to 375°F (190°C).
Transfer the pasta mixture to a greased casserole dish.
In a small bowl, mix the breadcrumbs (or crushed crackers) with Parmesan cheese and melted butter. Sprinkle this topping over the pasta.
Bake uncovered for 10–15 minutes, or until the topping is golden brown and crispy.
