Preheat oven to 350 degree F and grease a 13"x9" baking pan with cooking spray.
Bring a large pot of water to a boil. Scrub potatoes and place them, whole, into the boiling water. Cook for about 20 minutes. Remove from the water and let sit until cool enough to handle.
Meanwhile, make the cheese sauce. Melt butter in a medium saucepan over medium heat. Whisk in flour and cook, whisking constantly, until flour is golden brown; about 2 minutes. Stir in milk and cook, stirring often, until thickened; about 2-3 minutes. Remove from heat and stir in shredded cheese. Season with salt and pepper. If the sauce seems too thick, you can stir in up to 1/4 of a cup of milk.
Gently peel potatoes and slice into 1/8 inch rounds. Place 1/3 of the potatoes overlapping in a single layer in the baking dish, seasoning with salt and pepper. Top with about half of the ham. Spoon about 1/3 of the cheese sauce on top of the potatoes and ham.
Repeat with another layer of potatoes, ham and cheese sauce, then finish with a final layer of potatoes and pour all of the remaining cheese sauce over the top layer of potatoes. Spread to ensure all of the potatoes are covered.
Sprinkle with 1/4 cup shredded cheddar (if desired) and paprika (about 1/8-1/4 teaspoon).
Bake in the 350 degree oven for 20-25 minutes, or until sauce is bubbly.
Garnish with fresh minced chives and serve immediately.
Notes
Nutritional information is based on 6 large main course servings. If you plan to serve as a side dish, you could easily get 8-10 servings.
Storage
Refrigerate: Store leftovers in an airtight container in the refrigerator and these potatoes will last several days. You can reheat a large portion in the oven, or use a microwave for individual portions.Freeze: Cool the potatoes entirely and place in an airtight, freezer-safe container. You could also freeze them in the pan, then pop them out and wrap them in plastic wrap and foil. Freeze for up to 4-6 months.Reheat in the microwave: Best for single servings. Thaw in the fridge overnight. Place into the baking dish and cover with foil to keep them from drying out. Bake as the recipe directs.Reheat in the oven: Best for larger portions or more than one serving. Thaw in the fridge overnight. Place into a baking dish and cover with foil to keep the it from drying out. Bake at 350℉ for 15-20 minutes or until warmed through.