Creamy Vegan Dauphinoise Potatoes with Mushrooms

Name: Creamy Vegan Dauphinoise Potatoes with Mushrooms
Prep time: 15 min
Cook time: 50 min
Total time: 1 h 5 min
Cuisine: European, Mediterranean, French
Ingredients: 1 tablespoon olive oil; 2 onions, peeled, halved and thinly sliced; 2 cloves garlic, crushed (rub the roasting pan or baking dish with one of them, before crushing or finely grating it); 500g (18 oz) mushrooms, sliced; 500ml (2 full cups) mushroom soup (or creamy mushroom sauce, see notes); 500ml (2 full cups) vegan cream; 1 tablespoon dried parsley; 2 teaspoons dried basil; 2 pinches of salt and pepper; 2.5 kg (5 1/2 lbs) potatoes (I like floury potatoes, but waxy are ok too), peeled and thinly sliced