Preheat the oven to 375 degrees.
Bring a large pot of water to a boil and carefully add in the sliced potatoes. Parboil the potatoes for 5-7 minutes. Drain off the water.
In a large saucepan over medium heat add in the butter and allow it to melt.
Add in the onions and garlic and sautee until tender, for about 3-5 minutes. Stir in the flour until fully combined.
Add in the milk. salt, garlic powder, onion powder, and creole seasoning and stir until fully combined. Allow it to cook for 3-5 minutes then remove from the heat.
Coat your baking dish with nonstick cooking spray or butter.
At the bottom of your baking dish add a layer of the sauce. Then add a layer of the potatoes and top with the shredded cheddar and mozzarella cheese. Continue these steps until the baking dish is full.
Top with the remaining cheddar, and mozzarella cheese. Bake for 40 minutes and allow potatoes to rest for 10 minutes before serving.