1️⃣ Bring a large pot of salted water to a boil and cook the pasta according to the package directions. Drain and set aside.
2️⃣ In a large skillet, melt the butter over medium heat. Add the chopped onion and cook for 3-4 minutes until softened. Add the minced garlic and cook for another minute.
3️⃣ Sprinkle the flour over the onions and garlic, stirring to absorb. Slowly whisk in the chicken broth and heavy cream, bringing it to a simmer. Cook for 3-4 minutes until the sauce thickens slightly.
4️⃣ Stir in the frozen peas, carrots, corn, and cooked chicken. Season with thyme, salt, and pepper. Cook for 5 minutes until the vegetables are heated through.
5️⃣ Add the cooked pasta to the skillet and toss to coat in the creamy sauce. If using, stir in the shredded cheddar cheese until melted.
6️⃣ Garnish with fresh parsley and serve.