Preheat your oven to 350°F and generously grease a 3 quart (9×13) casserole dish with 1 Tbsp of butter.

In a large pot or Dutch oven, heat 4 Tbsp of butter over medium heat. Slowly whisk in flour for 2 minutes until combined. Gradually pour in the milk and cream, continuing to whisk. Season with salt, pepper, onion powder, and garlic powder to taste, and keep whisking until the sauce has thickened. Remove from heat and mix in half of the shredded cheese until melted.

Slice 1/8 inch thin potato rounds, either peeled or unpeeled. Stir the potato rounds into the cheese sauce, making sure they are well coated. Transfer the mixture to the prepared casserole dish and sprinkle the remaining grated cheese on top.

Bake the dish, covered with foil, for 60 minutes. Remove the foil and bake for an additional 15-30 minutes or until the top is golden brown and the potatoes are tender. If more browning is desired, broil for 1-2 minutes but keep a close eye to prevent burning. Allow the dish to rest for 15 minutes before serving. Garnish with chives and freshly cracked black pepper, if desired.