Using my stand mixer, combine the chicken, ham, butter, cream cheese, dijon mustard, lemon juice, salt, pepper, and onion powder.
In a lightly greased casserole dish, scrap the blended ingredients in and smooth out. Next, top with the swiss cheese. Cover with foil and place in a 350 degree oven. Bake for 20-30 minutes. (Longer if the dish was made ahead. You want everything hot and melty)
Remove the foil and place back into the oven with the broiler on to give the top a nice golden color. Usually about 5 more minutes.