Pre-heat oven to 350° F.

Grease with butter a 9x12" baking dish, set aside.
Slice the potatoes 1/8th of an inch thick, you will probably need a mandolin or slicer, however patience and a careful hand can slice them very close to the desired thickness.

Start the béchamel sauce by having the milk hot in one small sauce pan and staying warm on a low burner, do not let the milk boil, now in a separate sauce pan, add the flour and butter to a medium-low heat, once the mixture comes together, stirring, cook out the raw flour taste, you may lower the heat if the mixture is boiling too much.
After about 5-6 minutes of stirring, slowly add in the hot milk, a little at a time, using a whisk, until you have a smooth consistency. Now stir in the cheeses and nutmeg and salt and cook over medium heat until it thickens, about 7 minutes. Now stir in about 4-5 oz of the shredded cheese, once incorporated and smooth, remove from the heat and set aside.

Now add a layer of sliced potatoes to the bottom of the baking dish, sprinkle with salt and pepper. Now add a handful of shredded cheese, enough to have on top of the potatoes, but not completely cover. Remember we have a cheese sauce going in also! If your using ham you can layer on, just like the cheese in areas but don't smoother the potatoes as the cheese sauce needs to bubble through the layers, so tear up large slices of ham if your using it. Now repeat the process, a layer of potatoes, salt and pepper, some shredded cheese (and ham if using it).

At this point you can spoon in some of the béchamel sauce over the top and corners, you don't need to cover everything.

Keep layering, potatoes, salt and pepper, dash of shredded cheese (and ham if using) and a little sauce. When you put in your last potato slices sprinkle with salt and pepper finish with béchamel sauce over everything, corners and sides and now add the remaining shredded cheese across the dish, the béchamel will work its way down between the layers, Cover the baking dish with aluminum foil and bake for 1 hour.

After one hour remove the foil covering the dish and place the dish back in the oven, uncovered for an additional 30 minutes, after 16 minutes, if your using oily cheeses like cheddar and the sliced meats, you ,may want to use a paper towel and dab any grease pockets at the top. Return to the oven for an additional 15 minutes, if after that time the top is not as crusty and browned as you like, stick the dish under the broiler for a minute or two.

Serve and enjoy!