AU GRATIN POTATOES

4 – 5 large russet potatoes, 1 large white onions, thinly sliced into rings, 1 stick salted butter, 3 tablespoons cornstarch, ½ teaspoon salt, ¼ teaspoon black pepper, ¼ teaspoon yellow mustard, 2 ½ cups heavy whipping cream, 2 ½ cups shredded sharp cheddar cheese, ¼ cup softened cream cheese.

Heavily butter a casserole dish, set aside.  In a saucepan add the cheese, butter, cornstarch, mustard, whipping cream, cheddar cheese, and cream cheese.  Cook on medium heat until everything is melted and starts to thicken.  Add salt and pepper to taste, set aside.    Wash and peel the potatoes.  With a mandolin thinly slice the potatoes.  Layer the potatoes, overlapped, on the bottom of the dish.  Layer 1/3 of the onions on top of the potatoes pour 1/3 of the cream sauce over the potatoes and onions.  Repeat this process to the top of the casserole dish.  Bake, uncovered at 375 degrees for 90 minutes.