Cook the pasta according to package instructions until al dente. Drain and set aside.
2. Cook the chicken:
In a large skillet or Dutch oven, heat 2 tablespoons of olive oil or butter over medium heat. Add the diced chicken and cook until browned and cooked through, about 6-8 minutes. Season with salt and pepper to taste.
Once the chicken is cooked, remove it from the skillet and set it aside.
3. Sauté the vegetables:
In the same skillet, add the onion and cook for about 3-4 minutes until softened.
Add the garlic and cook for another 30 seconds until fragrant.
Add the frozen mixed vegetables and cook for an additional 3-4 minutes, until heated through.
4. Make the creamy sauce:
Sprinkle 1/4 cup flour over the vegetable mixture and stir to coat the vegetables evenly. Cook for 1-2 minutes to eliminate the raw flour taste.
Gradually add the chicken broth, stirring constantly to prevent lumps from forming. Cook until the mixture begins to thicken, about 3-4 minutes.
Stir in the milk (or cream) and bring the mixture to a simmer. Cook for another 2-3 minutes, until the sauce has thickened to your liking.
5. Add the cheese and combine:
Reduce the heat to low and stir in the shredded cheddar cheese. Continue stirring until the cheese has melted and the sauce is smooth.
Add the cooked chicken and pasta to the sauce, stirring to combine everything evenly. Cook for an additional 2-3 minutes, allowing the pasta to soak up some of the sauce and heat through.
6. Season and serve:
Taste the dish and adjust the seasoning with salt, pepper, and dried thyme. If you’d like, you can also sprinkle some fresh parsley on top for garnish.