Looking for a comfort-food potato gratin - with a twist? Ours has low FODMAP oyster mushrooms, too.
Heat remaining 2 tablespoons of oil in a large sautepan (I use a 3-quart/2.8 L) and heat over medium heat. Add chopped mushrooms and saute until softened, just a few minutes, then remove from heat. Set aside.
Add the potatoes to the saucepan then add the half-and-half, salt and generous amount of pepper. Bring to a vigorous simmer over medium heat, shaking the pan occasionally, and simmer for 3 minutes.
Carefully scoop and pour the mixture into prepared casserole dish. Gently coax the potatoes, mushrooms and liquid into an even layer. Sprinkle the cheese evenly over the top.