01 -
Heat the oven to 375°F (190°C).
02 -
Combine half of the Cheddar cheese and half of the French fried onions with the mashed potatoes. Press the mixture evenly onto the bottom and up the sides of a 2-quart casserole dish to create a shell.
03 -
In a separate bowl, mix the diced ham, thawed peas and carrots, cream of mushroom soup, dry mustard, granulated garlic, and black pepper until well combined.
04 -
Spoon the ham and vegetable mixture into the mashed potato shell. Cover the dish loosely with aluminum foil.
05 -
Bake in the preheated oven for 45 minutes.
06 -
Remove the foil, sprinkle the remaining Cheddar cheese and French fried onions over the top, and bake uncovered for an additional 5 minutes until the cheese is melted.
07 -
Remove from the oven and allow the casserole to rest for 5 to 10 minutes before serving.