Ham and Potato Casserole

INGREDIENTS:

6 small potatoes, peeled and cut into 1/2-inch cubes
7 tablespoons butter, divided
⅔ pound leftover cooked ham, cut into 1/2-inch cubes
1 small onion, finely chopped
3 tablespoons all-purpose flour
1 ½ cups milk
salt and ground black pepper to taste
1 (8 ounce) package shredded Cheddar cheese
¼ cup bread crumbs

DIRECTIONS:

Place potatoes into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, 10 to 15 minutes.
Meanwhile, preheat the oven to 350 degrees F (175 degrees C). Grease a 1 1/2-quart baking dish.
When the potatoes are almost finished, melt 3 tablespoons butter in a skillet over medium heat. Add ham and onion; cook and stir until the onion has softened and turned translucent, about 5 minutes. Remove from the heat.
Drain potatoes; add to the ham mixture and stir to combine. Transfer to the prepared baking dish.
Melt remaining 4 tablespoons butter in a saucepan over medium heat. Whisk in flour and stir until the mixture becomes paste-like and light golden brown, about 5 minutes …