Fill a large pot with water, add a generous pinch of salt, and bring it to a rolling boil. Add the rotini or fusilli pasta and cook according to the package instructions until al dente. Drain the pasta and set it aside, reserving a small amount of pasta water (about 1/4 cup) for later.
In the same pot, add olive oil and heat over medium heat until it shimmers. Add the diced cooked chicken to the pot and sauté for about 2-3 minutes, or until the chicken is warmed through.
Incorporate the frozen mixed vegetables into the pot, stirring them in for an additional 2 minutes, allowing them to soften slightly.
Sprinkle the all-purpose flour evenly over the chicken and vegetable mixture. Quickly stir to ensure everything is well-coated with the flour. Cook for an additional minute to eliminate the raw flour taste.
Gradually pour in the chicken broth while continuously stirring to prevent lumps from forming. Follow this by adding the whole milk, garlic powder, onion powder, dried thyme, salt, and pepper. Increase the heat to bring the mixture to a gentle simmer, cooking until it thickens, which should take about 3-5 minutes.
Once the sauce is thickened, add the drained pasta to the pot. Gently toss to combine, ensuring the pasta is thoroughly coated in the creamy mixture. If it's too thick, you can add a splash of the reserved pasta water to reach the desired consistency.
Lower the heat and stir in the shredded cheddar cheese. Continue stirring until the cheese is fully melted and the sauce is creamy and smooth.
Taste and adjust seasoning, adding more salt and pepper if necessary. Remove from heat.
Serve warm in bowls or on plates, garnished with a sprinkle of freshly chopped parsley for a pop of color and freshness.
Notes
For a cozy presentation, serve in individual cast-iron skillets or rustic bowls. Top each serving with a little extra grated cheese and parsley for an inviting look!