Prepare the Ingredients

1. Preheat Oven: Preheat your oven to 375°F (190°C).
2. Sauté Vegetables: In a large skillet, heat the olive oil over medium heat. Add the diced onion and garlic, cooking until softened, about 3-4 minutes.
3. Add Mushrooms: Stir in the sliced mushrooms and cook until they are golden and tender, about 5-7 minutes. Season with salt and pepper, then set aside.

Layer the Bake

1. Assemble the Layers: In a greased baking dish, layer half of the sliced potatoes at the bottom. Spread half of the sautéed mushroom mixture over the potatoes.
2. Add Cream: Pour half of the cream over the layers and sprinkle with half of the cheese.
3. Repeat Layers: Add the remaining potatoes, followed by the rest of the mushrooms, cream, and cheese.

Bake the Dish

1. Cover and Bake: Cover the baking dish with aluminum foil and bake in the preheated oven for 45 minutes.
2. Uncover and Brown: After 45 minutes, remove the foil and bake for an additional 10-15 minutes, or until the top is golden brown and the potatoes are tender when pierced with a fork.