Gather the ingredients. Preheat an oven to 350 degrees F (175 degrees C).

Grease one 9x13 inch baking pan with butter. Spread potatoes evenly in the pan.

Whisk together heavy cream, milk, garlic, flour, salt, and pepper in a large bowl. Pour cream mixture over the potatoes. Cover with foil.

Bake in the preheated oven for 20 minutes, then remove the foil. Continue baking until the potatoes are easily pierced with a fork, about 40 minutes.

Remove potatoes from the oven and sprinkle Cheddar cheese on top. Return to oven and bake until the cheese is melted, 5 to 10 minutes. Allow to cool for 5 minutes before serving.