Preheat oven to 350 degrees F. Grease a 2-quart rectangular baking dish; set aside.
For sauce, in medium saucepan cook onion in hot butter over medium heat 5 minutes or until tender; stirring occasionally. Stir in flour and mustard. Add milk all at once. Cook and stir over medium heat until slightly thickened and bubbly. Reduce heat to low. Whisk in Neufchatel cheese until smooth. Gradually add 1/2 cup of the Gruyere cheese until cheese is melted. Stir in chives.
In bowl combine potatoes, ham, and sauce; toss gently to combine. Transfer to prepared baking dish.
Bake, covered, 1 hour or until potatoes are tender. Uncover; stir carefully. Sprinkle with crushed chips and remaining cheese. Bake, uncovered, 10 to 15 minutes more or until cheese is melted. Let stand, 10 minutes before serving. Sprinkle with herbs. Serves 6.