Potatoes au Gratin with Mustard (Final)

Preheat oven to 400. Grease a 9 x 12 glass baking dish. Combine the chicken broth, whipping cream, and mustard until mustard has completely dissolved (best to add mustard to small amount of hot chicken broth and emulsify) then add remaining chicken broth and cream). Place potato slices in the dish to make an overlapping single layer. Sprinkle with 1/3 of the shredded Gruyere. Repeat with a second layer of potatoes. Repeat for the third layer of potatoes but pour the chicken broth combination over the potatoes evenly before sprinkling with cheese. Bake for 60-75 minutes until the the potatoes are cooked through and brown on top. May need to be tented with foil to prevent the cheese from burning.