01 - Bring a large pot of salted water to a rolling boil. Add the short pasta and cook according to package directions until al dente. Drain through a colander and set aside.
02 - While the pasta cooks, melt the butter in a large skillet or Dutch oven over medium heat. Add the diced onion and sauté until softened and translucent, about 2 to 3 minutes. Add the minced garlic and cook for an additional 30 seconds until fragrant.
03 - Sprinkle the all-purpose flour over the softened aromatics. Stir continuously for about 1 minute to cook out the raw flour taste and form a smooth roux.
04 - Gradually pour in the chicken broth and milk while whisking constantly to prevent lumps. Bring the mixture to a gentle simmer and let it thicken for 2 to 3 minutes, stirring occasionally.
05 - Stir in the dried thyme, dried parsley, salt, and black pepper. Add the frozen peas and carrots mix, frozen sweet corn, and cooked chicken. Continue cooking for 3 to 4 minutes until everything is heated through and the vegetables are tender.
06 - Add the drained pasta to the skillet and toss well to coat every piece evenly in the creamy sauce. Taste and adjust the seasoning with additional salt or pepper as needed.
07 - If using, stir in the shredded cheddar cheese until fully melted and the sauce is smooth and creamy. Serve immediately while hot, garnished with fresh parsley if desired.