Overlapping each slice, place a layer of sweet potatoes in the baking dish. Season this layer with salt and pepper. Repeat the layers five times, seasoning each layer with salt and pepper until you have six layers of sweet potatoes.
Pour the half & half and minced garlic into the dish; push down on potatoes to evenly distribute the half & half.
Cover the dish with aluminum foil and bake for 40 minutes. Carefully remove the foil.
Turn oven up to 400 degrees and cook uncovered for 20 minutes, or until golden brown on top and the gratin is not runny. The potatoes should absorb the half & half. Remove from oven and top with blue cheese.