Step 1

Whisk all ingredients for cream sauce together in a pitcher or small pot. Set aside

Step 2

Preheat the oven to 400°F then spray a 10x7 casserole dish with non-stick cooking spray. Ladle a small amount of cream sauce into the dish to lightly cover the bottom

Step 3

Peel the sweet potatoes then slice them to ⅛ inch thick on the mandolin slicer

Step 4

Layer the sweet potatoes in the bottom of the pan slightly overlapping each other. Stir the cream then ladle a small amount of cream sauce over the potatoes and sprinkle them lightly with Romano cheese

Step 5

Begin the next layer of sweet potatoes placing them in the opposite direction of the first layer. Ladle them with cream then a light sprinkle of Romano

Step 6

Continue this process until all potatoes and cream are used up. Press the potatoes down so that the cream covers the top of them

Step 7

Sprinkle the remaining Romano over the top of the dish then bake for 40 minutes, uncovered

Step 8

Place aluminum foil over the top of the dish then continue baking another 15 minutes

Step 9

Remove the sweet potato au gratin from the oven and allow to cool for about 30 minutes to set. Serve warm or at room temperature