Step 1

Preheat oven to 350°F (175°C). Lightly grease a 2-quart casserole dish to prevent sticking.

Step 2

Layer the ingredients: Arrange half of the sliced potatoes at the bottom of the dish, followed by half of the ham and half of the onions. Repeat with the remaining potatoes, ham, and onions, layering as desired.

Step 3

Prepare the sauce: In a medium saucepan, melt butter over medium heat. Stir in flour and cook for 1 minute, stirring constantly to eliminate the raw taste.

Step 4

Add the milk: Gradually whisk in the milk. Allow the mixture to simmer, stirring frequently, until it thickens. Season with salt, pepper, and paprika.

Step 5

Incorporate the cheese: Remove the sauce from heat and stir in the shredded cheddar until fully melted. Pour the sauce evenly over the layered potatoes, ham, and onions.

Step 6

Bake covered: Cover the dish with aluminum foil and bake for 60 minutes.

Step 7

Finish with Parmesan: Remove the foil, sprinkle Parmesan cheese over the top, and bake uncovered for an additional 20-30 minutes, or until bubbly and golden brown.

Step 8

Cool slightly before serving: Allow the dish to rest for a few minutes before serving to avoid burns and to let the flavors settle.