Preheat the oven to 375 F.
Lightly grease a 9x13 bake dish, and set it to the side.
Combine all the shredded cheeses in a large bowl, and set to the side.
Now toss 4 tbsp of butter into a large sauce pan, and place the plan over medium heat.
Once the butter has melted, sprinkle in 2 tbsp of all purpose flour.
Whisk the flour in with the butter, and cook for 2 minutes.
Pour in the half & half, and whisk in until everything is well combined.
Cook the half & half mixture until it has thickened, then add in half of the cheese mixture.
Stir in the cheeses until it's all melted, then add in the onion, garlic, and ham.
Sprinkle in the seasoning salt (I use my RosaMae Seasonings Seasoning Salt).
Stir everything, and let cook for 5 minutes, then turn off the heat,
Next, add half of the sliced potatoes into a 9x13. Pour half of the cheese sauce mixture on top of the potatoes, then sprinkle half of the remaining cheese on top.
Next, top with the remaining potatoes. Then repeat with th cheese sauce, then remaining cheese.
Leave everything uncovered, then place it it the oven.
Let bake for 50-55 minutes.
Remove from the oven, and let sit for 10-15 minutes before serving.
Sprinkle the top with fresh parsley.
Serve & enjoy!