In a large pot of salted boiling water, cook pasta according to package directions until al dente. Drain and set aside.
In a large skillet over medium heat, melt butter. Add garlic and cook until fragrant, about 2 minutes. Sprinkle in flour and cook until slightly golden, 2 minutes more. Pour in chicken broth and heavy cream and bring to a boil. Season with salt and pepper, then add mustard powder. Reduce heat to medium-low and simmer until liquid coats the back of a spoon, 10-12 minutes.
Remove skillet from heat and stir in cooked pasta, chicken, ham, and Gruyere. Sprinkle top with Parmesan.
Bake until warmed through, 13-15 minutes. For a golden top, broil for an extra 2-3 minutes. Garnish with parsley.
Recipe by The Best Video Recipes for All at https://recipes-for-all.com/chicken-cordon-bleu-skillet/