01 - Bring a large pot of salted water to a boil. Cook the short pasta 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, about 2 to 3 minutes. Add the minced garlic and cook for 30 seconds more until fragrant.
03 - Sprinkle the flour over the onion and garlic. Stir constantly for about 1 minute to cook out the raw flour taste and form a smooth roux.
04 - Gradually whisk in the chicken broth and milk, stirring until the mixture is smooth and free of lumps. Bring to a simmer and let the sauce 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. Cook 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 to coat evenly in the sauce. Taste and adjust salt and pepper as needed.
07 - If using, stir in the shredded cheddar cheese until fully melted and the sauce is creamy. Serve hot, garnished with extra fresh or dried parsley if desired.