In a large pot, bring water to a boil and add a pinch of salt. Add the rotini pasta and cook according to package instructions until al dente. Drain and set aside.
In a large skillet, heat olive oil over medium-high heat. Add the diced chicken breasts and season with salt and pepper. Cook until golden brown and cooked through, about 6-8 minutes.
Add the diced onion and minced garlic to the skillet. Cook for 2-3 minutes until the onion is translucent.
Stir in the frozen mixed vegetables, chicken broth, heavy cream, thyme, parsley, and flour. Cook on medium heat until the mixture thickens, about 5-7 minutes.
Incorporate the cooked rotini pasta into the skillet, stirring to combine all ingredients thoroughly.
If desired, transfer the mixture to a baking dish, sprinkle with shredded cheddar cheese and breadcrumbs, and bake at 350°F (175°C) for 15-20 minutes until golden and bubbly.
Serve hot, either directly from the skillet or the baked dish.