Step 1

Preheat oven to 350 degrees and grease a 9-inch by 13-inch baking dish.

Step 2

Slice the potatoes thin and add them to a large mixing bowl.

Step 3

Add the diced onions, salt, pepper, and ham to the bowl. Toss the ingredients.

Step 4

Pour the potato and ham into a greased baking dish and set aside.

Step 5

In a medium saucepan, add the butter and melt on medium heat.

Step 6

When the butter melts, add the flour and mix with a whisk. It will be lumpy.

Step 7

Pour the milk into the saucepan while whisking. Keep whisking until all the lumps are gone.

Step 8

Bring to a boil.

Step 9

Add the cheese and stir to melt.

Step 10

Pour the cheese mixture over the potatoes and ham. Take a spoon and move the potatoes around a little to help the cheese mixture get into all the grooves.

Step 11

Cover with aluminum foil and bake for 60 minutes or until the potatoes are tender.

Step 12

Remove the foil and bake for another 15-20 minutes.