Preheat oven to 400°F degrees.
In a small skillet, add olive oil and mushrooms and heat on medium for 5-6 minutes to let mushrooms release moisture. Remove from heat and set aside.
In a small sauce pan, heat cream with garlic and gorgonzola, until it is heated through, but not boiling. Season with salt and pepper.
Peel potatoes, cut into ⅛ slices and place some of the potatoes in a baking dish.
Pour half of the warm cream sauce over the potatoes. Sprinkle with grated cheese and add the mushrooms. Repeat these steps with the remaining ingredients.
Bake for 20-30 minutes or until browned and bubbly. Let gratin sit for 10 minutes before serving.
