This potato mushroom casserole is delicious as is, or you can serve with sour cream.
Preheat oven to 400 degrees F.
Heat 2 tablespoons of oil in a frying pan on the stovetop.
Add onions and cook over medium heat until soft (about 5 minutes).
Add mushrooms until they throw off their juices (about another 5 minutes).
Grease a large baking dish.
Put the onions and mushrooms with the juice into the baking dish.
Peel the potatoes and wash with cold water.
Cut potatoes lengthwise into 1/4 inch thick slices.
Place slices in a large bowl.
Add 4 tablespoons of olive oil, garlic, salt and pepper to bowl.
Toss the potatoes gently coating them with the mixture.
Once tossed, layer the potatoes on top of the onion and mushroom mix in the baking dish.
Cover the baking dish tightly with aluminum foil and bake for 30 minutes. Poke with a knife to test if baked through.
When done, remove the casserole from oven.
Turn the oven down to 350 degrees F.
Uncover the casserole and sprinkle the shredded cheese on top.
Bake about 15 minutes more, until the casserole turns golden brown.
Remove the casserole from the oven & let settle for 5 minutes before serving.