Begin by preparing the egg noodles to an al dente texture, adhering strictly to the directions provided on the packaging.

While the noodles are cooking, place a large skillet over medium-high heat and melt the butter. Once melted, add the diced onion and minced garlic to the skillet, along with the thawed peas and carrots. Season the mixture with kosher salt and black pepper. Sauté the vegetables until the onions have become soft and translucent, which should take approximately three minutes.

Sprinkle the flour evenly over the vegetables, stirring well to ensure it fully integrates with the butter and vegetables. This will create a roux that will help thicken the sauce in subsequent steps.

Gradually pour in the chicken broth, followed by the heavy cream, stirring continuously. Increase the heat to bring the mixture to a boil, then reduce the heat to maintain a gentle simmer. Continue to stir the sauce periodically as it simmers and thickens, approximately five minutes.

Drain the cooked noodles thoroughly and add them to the skillet, along with the diced chicken. Stir the contents of the skillet well to ensure the noodles and chicken are fully coated with the sauce. Taste the dish and, if necessary, adjust the seasoning with additional salt and pepper.

Serve the dish promptly while hot, ensuring a rich and creamy dining experience.